Igneous Rocks

1. Adakite

Adakite is a type of volcanic igneous rock that is typically high in silica and low in aluminium. It is named after Adak Island in Alaska, where it was first discovered. Adakites are typically associated with subduction zones, where oceanic crust is being subducted beneath a continental plate, and are thought to be generated by partial melting of the subducted oceanic crust.

Adakites are notable for their distinctive geochemical characteristics, including high aluminium and calcium content, low potassium content, and a particular ratio of isotopes of strontium and neodymium. These characteristics suggest that adakites are formed under high pressure and temperature conditions, such as those found at the base of the Earth’s crust.

Adakites are of interest to geologists because they provide important insights into the processes that occur at subduction zones and the formation of the Earth’s crust. They are also of interest to mineral explorers because some adakites can contain significant concentrations of copper and gold.

2. Adamellite

Adamellite is a type of igneous rock that belongs to the granitoid family. It is a coarse-grained rock that is composed mainly of plagioclase feldspar, potassium feldspar, and quartz, with small amounts of biotite, hornblende, and other minerals.

Adamellite is typically light grey to pink in colour and has a speckled appearance due to the various minerals in the rock. It is formed through the slow cooling and solidification of magma deep within the Earth’s crust and is often associated with other types of granitic rocks, such as granite and diorite.

The name “adamellite” comes from the Latin word “adamantinus,” which means diamond-like or unbreakable, and was first used by the geologist Joseph Paxson Iddings in 1909 to describe a specific type of granitic rock found in the Adirondack Mountains of New York. Today, the term is used more broadly to describe any granitic rock that has a similar mineral composition and texture to the original Adirondack rock.

3. Andesite

Andesite is a type of volcanic rock that is typically grey or dark in colour and has a fine-grained texture. It is named after the Andes mountain range in South America, where it is commonly found. Andesite is formed when magma from the Earth’s mantle rises to the surface and solidifies. It is composed of plagioclase feldspar, biotite, hornblende, and pyroxene minerals. Andesite is often used as a building material due to its durability and strength. It is also used in road construction, as an aggregate for concrete, and as a decorative stone.

 

4. Aphanite

Aphanite rock, also known as fine-grained rock, is a type of igneous rock that has a very fine-grained or compact texture. It is formed from lava that cools rapidly on the surface of the earth or beneath the earth’s crust. Aphanite rocks are made up of small mineral crystals that are not visible to the naked eye. This is because the crystals have no time to grow and are quickly solidified into a dense mass. Common examples of aphanite rocks include basalt, andesite, and rhyolite. Aphanite rocks are commonly used in construction and road building due to their hardness and durability.

4. Alkali feldspar granite

Alkali feldspar granite is a type of granite rock that contains high levels of alkali feldspar minerals. It is a plutonic rock that forms deep underground when magma cools and solidifies. Alkali feldspar granite typically has a coarse-grained texture, with individual feldspar crystals that are large enough to be visible to the naked eye. The colour of alkali feldspar granite can vary from pink to grey to white, depending on the number of different minerals present. This type of granite is commonly found in mountain ranges and other areas with high levels of geologic activity. It is often used in construction and as a decorative stone.

 

4. Anorthosite

Anorthosite is a type of igneous rock that is primarily composed of the mineral plagioclase feldspar. It is a coarse-grained rock that is typically light-coloured, with a crystalline texture. Anorthosite is found in a variety of geological settings, including the moon and other planets, as well as on Earth. It is often associated with large igneous intrusions and can be an important source of aluminium ore. Anorthosite has a number of interesting properties that make it useful for a variety of applications, including as a construction material, as a source of rare minerals, and as a potential site for future lunar mining operations.

5. Aplite

Aplite is a fine-grained igneous rock that is primarily composed of quartz and feldspar, with minor amounts of mica, hornblende, or other minerals. It is a type of granite that has a high concentration of quartz, which gives it a distinctive appearance and texture.

Aplite is formed when magma rises to the surface and cools, with the minerals crystallizing out in a specific order. The fine-grained texture of aplite is a result of the rapid cooling process that occurs near the surface.

Aplite can be found in various locations around the world, including the United States, Europe, and Asia. It is often used as a decorative stone for buildings and monuments, as well as for countertops and flooring. Its durability and resistance to weathering make it an ideal choice for outdoor applications.

Overall, aplite is a versatile and visually appealing igneous rock that is widely used in construction and design.

6. Basalt

Basalt is a dense, dark-coloured volcanic rock that is formed from solidified lava flows. It is a fine-grained, extrusive igneous rock that is typically composed of plagioclase feldspar, pyroxene, and sometimes olivine. Basalt is a common rock type on Earth and can be found in many places around the world. It is often used in construction as a building material, such as for roads, bridges, and monuments. Basalt can also be crushed and used for aggregate in concrete and asphalt. Additionally, it has been used for artistic purposes, such as for carvings and sculptures. Basalt can be found on other planetary bodies as well, such as the Moon and Mars.

6. Basaltic trachyandesite

Basaltic trachyandesite is a type of volcanic rock that is intermediate in composition between basalt and trachyte. It is a fine-grained rock that contains small crystals of plagioclase feldspar, pyroxene, and other minerals. The name basaltic trachyandesite comes from the fact that it contains more silica and alkalis than basalt, but less than trachyte. It is typically formed by the partial melting of the mantle in subduction zones or at hotspots, and it can be found in volcanic areas around the world. Some common examples of basaltic trachyandesite include the rocks found on the island of Hawaii and the Cascades of the Pacific Northwest.

Basaltic trachyandesite can be divided into several types based on their mineral composition, texture, and location of formation. Some of the types of basaltic trachyandesite are:

1. Olivine basaltic trachyandesite
2. Plagioclase basaltic trachyandesite
3. Pyroxene basaltic trachyandesite
4. Alkali basaltic trachyandesite
5. Dacitic basaltic trachyandesite
6. Hornblende basaltic trachyandesite
7. Andesitic basaltic trachyandesite.

The classification of basaltic trachyandesite can vary depending on the source, and it’s always advisable to refer to the latest scientific literature for accurate and up-to-date information.

7. Basanite

Basanite is a type of volcanic rock that is formed from basaltic magma. It is a fine-grained, dark-coloured rock that is composed of minerals such as plagioclase feldspar, pyroxene, and olivine. Basanite is often found in volcanic fields, such as those in Iceland and Hawaii. It is also known as tephrite, and can sometimes be confused with other volcanic rocks such as basalt and phonolite. Basanite is used in construction as a decorative stone and is also sometimes used for making tools and weapons.

8. Blairmorite

Blairmorite is a very rare porphyritic volcanic rock named after the community of Blairmore in southwestern Alberta, Canada. Blairmorite rock is a type of volcanic rock that is typically dark green or brown in colour. It is named after the town of Blairmore in Alberta, Canada, where it was first identified. Blairmorite is an intermediate to felsic volcanic rock, which means it contains a moderate to the high amount of silica. It is composed of various minerals, including plagioclase, hornblende, biotite, and quartz. Blairmorite is commonly found in volcanic areas, particularly in areas where the earth’s crust is being pulled apart, such as in rift zones and mid-ocean ridges. It is also commonly associated with other volcanic rocks such as rhyolite, dacite, and andesite.

9. Boninite

Boninite is a type of rare and unusual volcanic rock that is characterized by its low silica content, high magnesium and iron content, and high levels of incompatible elements like titanium and zirconium. It is believed to form at the edges of tectonic plates where the Earth’s mantle is melting and producing new crust.

The name boninite comes from the Bonin Islands, a group of volcanic islands located about 1000 kilometres south of Tokyo, Japan. The first boninite samples were collected from these islands in the early 20th century and were found to have a distinct chemical composition that was unlike any other known volcanic rock.

Boninite is believed to form from a type of magma called boninite magma, which is produced by the partial melting of the Earth’s mantle at depths of around 70-100 kilometres. This magma is highly depleted in silica and other elements that are normally found in magma, which gives boninite its unique chemical composition.

Boninite is a rare rock type and is found in only a few places around the world, including the Bonin Islands, the Mariana Islands, New Zealand, and parts of the western United States. It is of great interest to geologists and volcanologists as it provides important clues about the Earth’s mantle and the processes that drive plate tectonics.

10. Carbonatite

Carbonatite is a type of intrusive igneous rock that is dominated by carbonate minerals, particularly calcite and dolomite. It is relatively rare and makes up only a small percentage of the Earth’s crust. Carbonatite is believed to originate from the mantle, and its formation is thought to be related to the melting of carbonated rocks. It typically contains other minerals, such as apatite, magnetite, and phlogopite, and can also contain rare earth elements, niobium, and tantalum. Due to its rare mineral content, carbonatite is often a target for mining and exploration.

11. Charnockite

Charnockite is a type of granite rock that is composed of orthopyroxene, plagioclase feldspar, and quartz. It is named after Job Charnock, an English merchant who founded the city of Kolkata (formerly known as Calcutta) in India, where the rock is found in abundance. Charnockite is a hard and dense rock that has a characteristic speckled appearance due to the presence of dark-coloured orthopyroxene crystals. It is used as a decorative stone in construction and as an ornamental stone in jewellery making. Charnockite is also used as a source of crushed stone for road construction and as a raw material for the production of cement.

12. Enderbite

Enderbite is a type of igneous rock that forms from the cooling and solidification of magma or lava. It is typically composed of plagioclase feldspar and pyroxene minerals, and may also contain other minerals such as olivine and amphibole.

Enderbite has a dark, fine-grained texture and is usually found in the form of dikes, sills, or intrusive bodies in larger rock formations. It is commonly associated with volcanic activity and is often found in areas where there has been extensive lava flow.

Enderbite has a variety of uses, including as a building material, decorative stone, and in the production of crushed stone and gravel for construction projects. Its durability and resistance to weathering make it a popular choice for outdoor applications.

13. Dacite

Dacite is a volcanic rock that has an intermediate composition between felsic and mafic rocks. It is a type of igneous rock that is primarily composed of plagioclase feldspar, quartz, and biotite, with lesser amounts of hornblende, pyroxene, and other minerals.

Dacite is typically formed by the solidification of molten magma that has a composition between andesite and rhyolite. It can form in a variety of settings, including subduction zones, volcanic arcs, and hotspots. Dacite magma typically has a high viscosity, which means it is relatively slow-moving and can lead to explosive eruptions.

Because of its high silica content and slow cooling rate, dacite tends to have a fine-grained texture and can often contain phenocrysts, which are large crystals that are embedded in the fine-grained matrix of the rock. Dacite is commonly used in construction and as a decorative stone due to its attractive appearance and durability.

14. Diabase/dolerite

Diabase, also known as dolerite, is a dark-coloured igneous rock that is composed mainly of plagioclase feldspar, pyroxene, and sometimes olivine. It is typically fine-grained and often forms massive intrusions or sills. It is commonly found in dikes, sills, and volcanic plugs, and is often associated with basaltic rocks. Diabase/dolerite is a relatively hard and durable rock, making it suitable for use as a building and paving stone. It is also used as an aggregate in concrete and road construction. In addition, diabase/dolerite can be used as a decorative stone in landscaping and in the production of gravestones and monuments.

15. Diorite

Diorite is a coarse-grained igneous rock that is made up of plagioclase feldspar, biotite, hornblende, and sometimes small amounts of quartz. It is typically grey or black in colour, with a speckled appearance due to the contrasting colours of the mineral grains.

Diorite is formed when magma or lava cools and solidifies underground, and it is often found in the lower layers of volcanic and plutonic rock formations. It is commonly used as a building stone and is also used in road construction and as an aggregate in concrete.

Some notable examples of diorite being used in construction include the ancient Egyptian temples at Abu Simbel and the cathedrals of Canterbury and Durham in England.

16. Napoleonite

Napoleonite rock is a type of volcanic rock that contains plagioclase feldspar, pyroxene, and olivine minerals. It is named after Napoleon Bonaparte, as it was first identified in the island of Elba, where Napoleon was exiled in 1814. Napoleonite rock is typically dark-coloured and dense, with a fine-grained texture. It is formed through the solidification of magma and can be found in volcanic areas around the world. Although it is not a common rock, it has some industrial uses, such as in the construction of roads and as an abrasive material.

17. Dunite

Dunite is a type of ultramafic igneous rock composed almost entirely of olivine mineral. It is typically green in color and has a very high melting point, making it resistant to weathering and erosion. Dunite is commonly found in ophiolites, which are fragments of oceanic crust that have been thrust up onto land during tectonic activity. It is also used as a refractory material in high-temperature applications, such as furnace linings and crucibles. Due to its high olivine content, dunite is sometimes considered a potential source of magnesium, which is used in a variety of industrial applications.

18. Essexite

Essexite is a type of igneous rock that is primarily composed of plagioclase feldspar, pyroxene, and olivine. It is named after Essex County, New York, where it was first identified. Essexite is typically coarse-grained and has a dark colour, ranging from black to dark green. It is classified as a member of the gabbro family of rocks and is often found in association with other igneous rocks, such as diorite and granodiorite. Essexite is believed to have formed through the solidification of magma deep beneath the Earth’s surface, and it is often associated with areas of volcanic activity. It is commonly used as a building stone and as a decorative stone in landscaping.

19. Foidolite

It is a type of igneous rock that is rich in feldspathoids (FOIDs), such as nepheline, sodalite, and hauyne. Foidolite is usually dark-coloured, and fine-grained, and contains small crystals of feldspar, pyroxene, and olivine. It is formed from the solidification of magma that has a low silica content and a high concentration of alkali and alkaline earth elements. Foidolite is commonly found in alkaline volcanic and plutonic rocks, including carbonatites and kimberlites.

20. Gabbro

Gabbro is a coarse-grained, intrusive igneous rock that is composed of plagioclase feldspar, pyroxene, and sometimes olivine. It is typically dark-coloured, with a granular texture and a composition that is similar to basalt. Gabbro is formed deep within the Earth’s crust as magma cools and solidifies slowly over millions of years. It is commonly found in large plutons or intrusions that are exposed at the surface through erosion or tectonic uplift. Gabbro is widely used as a construction material, particularly for buildings and monuments. It is also used as a dimension stone for countertops, flooring, and decorative features.

21. Granite

22. Granodiorite

Granodiorite is a coarse-grained intrusive igneous rock that is composed of plagioclase feldspar, quartz, and biotite or hornblende. It is similar to granite in mineral composition but has a higher percentage of plagioclase feldspar than potassium feldspar. Granodiorite typically has a speckled appearance due to the different colours of the minerals that make up its composition. It is commonly found in mountainous regions and is used in construction as a building stone or crushed for road construction.

23. Granophyre

Granophyre is a type of igneous rock that is composed of both coarse-grained and fine-grained mineral crystals. It is considered to be an intermediate rock type between granite and diorite. Granophyre is often characterized by its distinctive texture, which consists of larger feldspar crystals surrounded by smaller mineral crystals.

The formation of granophyre typically occurs deep within the Earth’s crust, as magma slowly cools and solidifies over a long period of time. This slow cooling process allows for the formation of both large and small mineral crystals, creating the unique texture and appearance of granophyre.

Granophyre is commonly used in construction as a building material, as it is both strong and durable. It is also used in the production of decorative objects such as jewellery and ornamental carvings.

24. Harzburgite

Harzburgite is a type of ultramafic rock that is primarily composed of olivine and orthopyroxene, with minor amounts of clinopyroxene and spinel. It is commonly found in the Earth’s mantle and is thought to represent the residue left behind after the extraction of basaltic magma. Harzburgite is named after the Harz Mountains in Germany, where it was first described. It is a common rock type in ophiolites, which are slices of oceanic crust and mantle that have been uplifted and exposed on land. Harzburgite is also found in some areas of the continental lithosphere, such as the Kaapvaal Craton in South Africa.

25. Hornblendite

Hornblendite is a rock that is primarily composed of the mineral hornblende, which is a type of amphibole. Hornblende is a complex silicate mineral that can contain a variety of elements including magnesium, iron, calcium, aluminium, and sodium. Hornblendite is typically a dark green or black rock that has a granular texture, and it is usually found in metamorphic or igneous rocks. It is a common component of gabbro and diorite, and can also occur in ultramafic rocks such as peridotite. Hornblendite can be used as a construction material, but it is not commonly used for this purpose due to its relatively high cost and low availability.

26. Hyaloclastite

Hyaloclastite is a volcanic rock formed by the rapid cooling and solidification of lava when it comes into contact with water or ice. This type of rock is typically found in a submarine or subglacial environments, where molten lava flows into water or ice and solidifies into glassy fragments. Hyaloclastite is typically composed of volcanic glass shards, pumice, and other volcanic debris, which are often embedded in a matrix of fine-grained basalt or tuff. This rock is usually black or dark grey in colour and has a glassy or frothy texture. It is often used as an indicator of past volcanic activity in areas that are now covered by water or ice.

27. Icelandite

Icelandite is a type of basaltic volcanic rock found in Iceland. It is composed primarily of plagioclase feldspar and pyroxene minerals, with small amounts of olivine and magnetite. The rock is dark grey to black in colour and has a fine-grained texture. Icelandite is formed by the solidification of lava flows that erupted from fissure vents in Iceland’s volcanic landscape. It is often used as a building material in Iceland and has been used for centuries to construct homes and other structures. The unique properties of Icelandite make it a durable and long-lasting building material that is well-suited for Iceland’s harsh climate.

28. Ignimbrite

Ignimbrite is a type of volcanic rock formed from the rapid cooling and solidification of a hot mixture of volcanic ash, pumice, and gas, known as a pyroclastic flow. These flows can occur during explosive volcanic eruptions, where the volcanic material is violently ejected from the vent and cascades down the sides of the volcano, often accompanied by ash and gas clouds.

As the pyroclastic flow moves away from the vent, the hot mixture begins to cool and solidify, forming a dense and welded rock called ignimbrite. Ignimbrites can vary in composition and texture, but they are typically fine-grained and often display characteristic welding textures, such as flattened pumice fragments and aligned ash particles.

Ignimbrites are important geological formations, providing a record of ancient volcanic activity and the associated environmental conditions. They can also be valuable resources for the construction industry, as they are commonly used as building stones and road materials.

29. Ijolite

Ijolite is a rare igneous rock that is composed mainly of sodium-rich pyroxene and nepheline, with lesser amounts of plagioclase feldspar and other minerals. It is typically dark grey or black in colour and has a fine-grained or glassy texture. Ijolite is found in alkaline intrusions, such as those associated with carbonatites and kimberlites, and is believed to form at great depths in the Earth’s mantle. It is named after the Ijo people of Nigeria, where it was first described. Ijolite is not commonly used as a building material or in industry, but it is of scientific interest to geologists studying the composition and evolution of the Earth’s mantle.

15. Kenyte

Kenyte is a type of igneous rock. More specifically, it is a variety of porphyritic phonolite or trachyte with rhomb-shaped phenocrysts of anorthoclase with variable amounts of olivine and augite in a glassy matrix; the glass may be devitrified.

It was originally described and named by J. W. Gregory in 1900 for its occurrence on Mount Kenya. Kenyte has also been reported from Mount Kilimanjaro (Tanzania) and Mount Erebus (Antarctica).

30. Kimberlite

Kimberlite is a rare, ultramafic volcanic rock that is known for containing diamonds. It is named after the town of Kimberley in South Africa, where it was first discovered in the late 19th century. Kimberlite is formed deep within the Earth’s mantle and is brought to the surface through volcanic eruptions. The rock is typically dark in color and contains a variety of minerals, including olivine, pyroxene, and phlogopite. While diamonds are the most well-known mineral associated with kimberlite, it can also contain other valuable minerals such as chromium, garnet, and spinel. Kimberlite deposits are found in various regions around the world, including Canada, Russia, Australia, and Africa.

31. Komatiite

Komatiite is a rare and unusual type of volcanic rock that is believed to have formed from extremely hot lava, with temperatures ranging from 1,400 to 1,600 degrees Celsius. This type of rock is typically found in Archean-age greenstone belts, which are some of the oldest geological formations on Earth, dating back more than 2.5 billion years.

Komatiites are named after the Komati River in South Africa, where the first known occurrence of the rock was discovered. They are typically characterized by their high magnesium and low silica content, which gives them a distinctive appearance and unique chemical composition. They often have a distinctive spinifex texture, which is formed by the rapid cooling of the lava on the surface of the flow.

The formation of komatiites is thought to be related to the unique tectonic and geothermal conditions of the Archean Earth. As the planet cooled over time, the mantle became less capable of producing the extremely hot lava needed to form komatiites. Today, komatiites are a rare find, and they offer valuable insights into the geological history of the early Earth.

17. Larvikite

Larvikite is an igneous rock, specifically a variety of monzonite, notable for the presence of thumbnail-sized crystals of feldspar. These feldspars are known as ternary because they contain significant components of all three endmember feldspars. The feldspar has partly unmixed on the micro-scale to form a perthite, and the presence of the alternating alkali feldspar and plagioclase layers gives its characteristic silver-blue schiller effect (called labradorescence) on polished surfaces. Olivine can be present along with apatite, and local quartz. Larvikite is usually rich in titanium, with titanaugite and/or titanomagnetite present.

Larvikite occurs in the Larvik Batholith (also called the Larvik Plutonic Complex), a suite of ten igneous plutons emplaced in the Oslo Rift (Oslo Graben) surrounded by ~1.1 billion-year-old Sveconorwegian gneisses. The Larvik Batholith is of Permian age, about 292–298 million years old. Larvikite is also found in the Killala Lake Alkalic Rock Complex near Thunder Bay in Ontario, Canada.

The name originates from the town of Larvik in Norway, where this type of igneous rock is found. Many quarries exploit larvikite in the vicinity of Larvik.

32. Lamproite

Lamproite is a rare, ultramafic volcanic rock that is rich in potassium and other minerals such as diamonds, pyroxene, olivine, and phlogopite. It is a type of igneous rock that forms deep within the Earth’s mantle and is typically found in cratonic areas, such as the Kimberley region of Western Australia and the Colorado Plateau in the United States.

Lamproites are unusual rocks in that they are often found in small, isolated volcanic pipes or vents, rather than in large, extensive lava flows like most other volcanic rocks. These pipes or vents can contain valuable mineral deposits such as diamonds, which are formed under high pressure and temperature conditions deep within the Earth’s mantle.

The origin of lamproites is still not fully understood, but it is thought to be related to the upwelling of deep mantle material that forms hot spots beneath the Earth’s crust. These hot spots can trigger the formation of volcanic pipes or vents, which then bring the lamproite to the Earth’s surface. The rarity and unusual composition of lamproite make it an important object of study for geologists and mineralogists.

33. Lamprophyre

Lamprophyre is a type of igneous rock that is typically composed of feldspar, mica, amphibole, and biotite. It has a fine-grained texture and is often found in small intrusions or dykes. Lamprophyre is generally dark in color, ranging from black to dark green or brown, and can be found in many parts of the world, including North America, Europe, and Australia. It is formed by the partial melting of the Earth’s mantle and is often associated with volcanic activity. Lamprophyre is not widely used as a building material, but it has been used in some decorative applications due to its unique appearance.

34. Latite

Latite is a type of volcanic rock that is intermediate in composition between basalt and rhyolite. It is typically dark grey to black in colour and has a fine-grained texture. Latite is formed from magma that has a moderate amount of silica content, and it often contains phenocrysts (large crystals) of feldspar and mica. Latite is commonly found in volcanic regions and is used in construction, as a building stone, and for road surfacing. It is also used as an ornamental stone in jewellery and sculptures.

35. Lherzolite

Lherzolite is a type of ultramafic rock that is primarily composed of olivine, orthopyroxene, and clinopyroxene. It is a common rock found in the Earth’s upper mantle and is often associated with the formation of diamonds. Lherzolites are named after the Lherz region of France, where they were first described in the late 19th century. These rocks are usually formed by the partial melting of peridotite, which is another type of ultramafic rock. Lherzolites have a characteristic greenish-grey colour and a coarse-grained texture. They are also known for their high melting point, which makes them an important rock type in the study of the Earth’s mantle and its geological processes.

21. Mangerite

Mangerite is a metamorphosed plutonic intrusive igneous rock, that is essentially a hypersthene-bearing monzonite. It often occurs in association with norite, anorthosite, charnockite and rapakivi granite in Proterozoic metamorphic belts. It is characterised by the presence of mesoperthite. It was named for Manger, Norway, by Carl Fredrik Kolderup in 1903.

22. Minette

A lamprophyre containing phenocrysts of phlogopite-biotite and occasionally amphiboles in a groundmass of the same minerals plus orthoclase and minor plagioclase. Mg-olivine and diopsidic pyroxene may also be present.

It is a hypabyssal igneous rock characterised by abundant biotite phenocrysts and/ or groundmass, lacking felsic phenocrysts, usually occurring in dykes.

The name is also used in France and Germany for oolitic ironstones, see Minette (ore).

36. Monzogranite

Monzogranite is a type of intrusive igneous rock that is composed of mostly quartz, plagioclase feldspar, and potassium feldspar. It is a coarse-grained rock that is formed deep within the Earth’s crust through the slow cooling and solidification of magma. Monzogranite is known for its light-coloured appearance and typically contains small amounts of other minerals such as mica, amphibole, and biotite. It is commonly found in mountainous regions and is often used as a building material due to its strength and durability.

37. Monzonite

Monzonite is an intrusive igneous rock that is medium to coarse-grained with a texture that ranges from equigranular to porphyritic. It is composed of plagioclase feldspar, orthoclase feldspar, biotite, hornblende, and quartz. Monzonite is similar in composition to syenite but has a higher content of plagioclase feldspar. It is often found in association with other igneous rocks such as granite, diorite, and gabbro. Monzonite can be found in various colours such as grey, green, and pink, depending on the mineral composition. It is commonly used as a decorative stone, as a building material, and in the production of countertops and tiles.

38. Nepheline syenite

Nepheline syenite is a type of igneous rock that is primarily composed of feldspar minerals such as nepheline and orthoclase. It is commonly found in alkaline intrusive complexes and is often associated with other igneous rocks such as granite and gabbro. Nepheline syenite is generally light-coloured and has a coarse-grained texture, with individual mineral grains that are easily visible to the naked eye. It is used in a variety of industrial applications, such as in the production of glass, ceramics, and paint, due to its low melting point and high levels of alkaline oxides. It is also used as a substitute for feldspar in some applications, as it is more economically viable and easier to obtain.

39. Nephelinite

Nephelinite is a type of volcanic rock that is composed primarily of clinopyroxene, olivine, and sometimes leucite or nepheline. It is typically dark in colour, with a fine-grained texture, and has a low silica content. Nephelinite is often associated with intraplate volcanism, meaning it is found in areas far from tectonic plate boundaries, such as hotspots or continental rifts. It is named after the Greek word “nephele,” which means cloud, because of its characteristic cloud-like appearance when it erupts as ash. Nephelinite is relatively rare, and its eruption style is generally not explosive.

40. Norite

Norite is a mafic intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite, orthopyroxene, and olivine. The name norite is derived from Norge, the Norwegian name for Norway.

Norite is also known as orthopyroxene gabbro. Norite may be essentially indistinguishable from gabbro without thin section study under the petrographic microscope. The principal difference between norite and gabbro is the type of pyroxene of which it is composed. Norite is predominantly composed of orthopyroxenes, largely high magnesian enstatite or an iron-bearing intermediate hypersthene. The principal pyroxenes in gabbro are clinopyroxenes, generally medially iron-rich augites.

Norite occurs with gabbro and another mafic to ultramafic rocks in layered intrusions which are often associated with platinum orebodies such as in the Bushveld Igneous Complex in South Africa, the Skaergaard igneous complex of Greenland, and the Stillwater igneous complex in Montana. Norite is also the basal igneous rock of the Sudbury Basin complex in Ontario, which is the site of a comet impact and the world’s second-largest nickel mining region. 

Norite is a common rock type of the Apollo samples. On a smaller scale, norite can be found in small localized intrusions such as the Gombak norite in Bukit Batok, Singapore. It is also plentiful in the Egersund intrusion area of southwestern Norway, with titanium deposits to the east.

41. Obsidian

Obsidian is a naturally occurring volcanic glass that forms when lava cools quickly. It is usually black or dark green in colour, but can also be brown, red, or grey. Obsidian is known for its sharp edges and was used by early humans for making tools and weapons. It is still used today for making knives, blades, and other cutting tools. Obsidian is also used in jewellery making and as a decorative stone. It is found in areas with past or present volcanic activity, such as the western United States, Iceland, and Italy.

42. Pegmatite

Pegmatite is a type of igneous rock that is characterized by its large-grained, coarse texture. It is composed of a variety of minerals, including feldspar, quartz, and mica. Pegmatites are formed from the slow cooling of magma, which allows for the growth of large crystals.

Pegmatites are often found in association with granite and other intrusive rocks. They can be found in a variety of geological settings, including mountain ranges, volcanic arcs, and deep-sea ridges.

Due to their unique mineral composition and large crystal size, pegmatites are often sources of rare and valuable minerals, such as lithium, tantalum, and beryllium. They are also used as a source of decorative stones and gemstones, such as tourmaline and aquamarine.

Overall, pegmatites are an important geological resource, providing valuable minerals and insights into the formation and evolution of the Earth’s crust.

43. Peridotite

Peridotite is a dense, coarse-grained, intrusive igneous rock composed mostly of the minerals olivine and pyroxene. It is typically dark green to greenish-black in colour and has a high density due to the abundance of heavy minerals. Peridotite is the most common rock type in the Earth’s upper mantle and is often found in orogenic belts, where tectonic forces have pushed it to the surface. It is also the main source of diamonds, as diamonds are formed from carbon under high pressure and temperature in the Earth’s mantle. Peridotite is not commonly used as a building material due to its density and lack of decorative properties, but it is used in industry for its high melting point and resistance to corrosion.

44. Phonolite

Phonolite is an igneous rock that is composed primarily of alkali feldspar and nepheline. It is a volcanic rock that forms from magma that is rich in silica and alkali metals, such as sodium and potassium. Phonolite is typically gray or brown in colour and has a fine-grained, porphyritic texture. It is commonly found in volcanic areas and is often associated with other volcanic rocks, such as tuff and pumice. Phonolite is used in construction and as an ornamental stone, and it is also used as a source of potassium and other minerals.

45. Phonotephrite

Phonotephrite is a type of volcanic rock that falls within the tephrite series. It is composed of feldspathoids, pyroxenes, and plagioclase feldspar. Phonotephrite typically has a fine-grained, porphyritic texture, meaning that it contains larger crystals (phenocrysts) within a finer-grained matrix.

The name “phonotephrite” comes from the Greek words “phono,” meaning sound, and “tephra,” meaning ash. This name reflects the fact that phonotephrite can produce a distinctive ringing sound when struck, due to its porosity and composition.

Phonotephrite is typically associated with alkaline volcanic activity, such as that found in rift zones or near subduction zones. It can also be found in intrusions, such as dikes or sills. Phonotephrite is relatively uncommon compared to other types of volcanic rocks and is not widely used in industry or construction.

46. Picrite

Picrite is an igneous rock that is composed mostly of olivine and pyroxene minerals. It is a mafic rock, meaning that it is rich in iron and magnesium, and has a high density. Picrite is usually green in colour due to the abundance of olivine, and it may also contain other minerals such as plagioclase feldspar, ilmenite, and chromite. Picrite is commonly found in volcanic and plutonic settings and is thought to form from the partial melting of the Earth’s mantle. It is an important rock type in the study of petrology and geology.

47. Porphyry

Porphyry is an igneous rock that is commonly used as a decorative stone in buildings and construction. It is characterized by its large, visible crystals, which are usually set in a fine-grained matrix of minerals. The crystals are typically feldspar, quartz, or mica, and they can be of various colours, including red, purple, blue, green, or yellow. Porphyry is formed from magma that has cooled slowly underground, allowing large crystals to form. It is often used as a paving material or as cladding on buildings, and it is known for its durability and resistance to weathering. Porphyry deposits are found in many parts of the world, including Italy, Mexico, and the United States.

48. Pumice

Pumice is a light, porous volcanic rock that is formed from frothy lava that solidifies quickly when ejected from a volcano. It is typically light grey or beige in colour and has a low density due to the presence of many air pockets within the rock. Pumice is commonly used as an abrasive material for polishing and cleaning, as well as in horticulture to improve soil drainage and aeration. It is also used in construction and as an insulating material due to its lightweight and heat resistance. Pumice is found in many volcanic regions around the world, including in Italy, Greece, the United States, and New Zealand.

49. Pyroxenite

Pyroxenite is a rock composed mainly of the mineral pyroxene. It typically contains less than 10% of other minerals, such as olivine, plagioclase, and magnetite. Pyroxenites are usually found as small intrusions within larger igneous bodies, such as gabbros and peridotites. They are typically dark green or black in color and have a coarse-grained texture. Pyroxenites are important sources of nickel, platinum, and chromium, which are used in various industrial applications. They are also used as a source of high-quality aggregate in construction projects.

50. Quartz diorite

Quartz diorite is a type of igneous rock that is composed of approximately equal amounts of quartz, plagioclase feldspar, and biotite. It is often used as a decorative building stone due to its striking appearance, which is characterized by a speckled pattern of grey and white grains. Quartz diorite forms deep underground through the slow cooling and solidification of magma and is commonly found in areas with extensive igneous activity, such as volcanic arcs and rift zones. It is a durable and hard-wearing material, making it suitable for use in a variety of construction applications.

51. Quartz monzonite

Quartz monzonite is a type of igneous rock that is composed mainly of quartz, plagioclase feldspar, and alkali feldspar. It has a medium-grained texture, with visible crystals of feldspar and quartz, and may also contain other minerals such as biotite, hornblende, and pyroxene.

Quartz monzonite is typically formed through the slow cooling and solidification of magma in the Earth’s crust, and can be found in a variety of settings, including intrusive plutons, dikes, and sills. It is often associated with other types of granitic rocks, such as granodiorite and tonalite.

Quartz monzonite is a durable and hard rock and is often used in construction and as a decorative stone. It is also used in geology as an indicator of the age and composition of the Earth’s crust.

52. Quartzolite

Quartzolite or silexite is an intrusive igneous rock, in which the mineral quartz is more than 90% of the rock’s felsic mineral content, with feldspar at up to 10%. Typically, quartz forms more than 60% of the rock, the rest being mostly feldspar although minor amounts of mica or amphibole may also be present. Quartzolite occurs as dykes, sills, veins, bosses and segregation masses;^[3][4] it is also found in association with greisen and pegmatite. Quartzolite is an extremely rare type of rock. No extrusive rock equivalent of quartzolite is known.

53. Rhyodacite

Rhyodacite is a fine-grained volcanic rock that is intermediate in composition between dacite and rhyolite. It typically contains 62-68% silica and is characterized by its light colour, high viscosity, and explosive eruptive behaviour. Rhyodacite is formed when magma with an intermediate composition is cooled and solidified at or near the Earth’s surface. It is commonly found in volcanic arcs, andesitic stratovolcanoes, and volcanic domes. Rhyodacite is used as a construction material, as decorative stone, and in the production of ceramics and glass.

53. Rhyolite

Rhyolite is an igneous rock that is light-coloured, fine-grained and has a high silica content. It is typically composed of quartz, feldspar, and mica minerals. Rhyolite is formed from volcanic magma or lava that has cooled and solidified quickly on the Earth’s surface. It is commonly found in volcanic areas and is often associated with other volcanic rocks such as andesite and basalt. Rhyolite can have a variety of textures and colours, ranging from light grey to pink or red, and can be porphyritic, meaning it has large crystals in a fine-grained matrix. It is used in construction, as a decorative stone, and as a material for making tools and weapons.

54. Scoria

s rapidly cooled, resulting in a porous and lightweight rock. Scoria is typically dark in color, ranging from black to dark red, and can have a vesicular texture due to gas bubbles that were trapped during its formation.

Scoria is commonly used in landscaping and construction projects, as it is lightweight and has good drainage properties. It is also used as a decorative element in gardens and in the construction of retaining walls. Additionally, scoria can be crushed and used as an aggregate in concrete and road construction.

In some parts of the world, scoria is also used for traditional building construction. For example, in Ethiopia, scoria is used to construct low-cost housing due to its lightweight and insulating properties.

55. Shonkinite

Shonkinite is a type of volcanic rock that is typically black or dark grey in colour. It is composed of olivine, pyroxene, plagioclase, and magnetite minerals. Shonkinite is typically found in intrusions or dikes associated with other volcanic rocks and is often associated with the mantle or deep crustal magmatic systems. The name “shonkinite” comes from the Shonkin Sag laccolith in Montana, where the rock was first identified.

56. Sovite

Sovite is the coarse-grained variety (or facies) of carbonatite, an intrusive, igneous rock. The finer-grained variety of carbonatite is known as alvikite. The two varieties are distinguished by minor and trace element compositions. Sovite is often a medium-to-coarse-grained calcite rock with variable accessory amphibole, biotite, pyrite, pyrochlore and fluorite.

57. Syenite

Syenite is a type of intrusive igneous rock that is primarily composed of feldspar minerals, with lesser amounts of other minerals such as hornblende, biotite, and pyroxene. It is similar in composition to granite, but contains more alkali feldspar and lacks the quartz that is typically present in granite.

Syenite is typically coarse-grained and has a granular texture. It is usually light in colour, ranging from grey to pink, and can sometimes have a porphyritic texture with larger crystals of feldspar or other minerals embedded in a finer-grained matrix.

Syenite is formed through the solidification of magma or lava beneath the Earth’s surface. It is often associated with other igneous rocks such as granite and diorite, and can be found in a variety of geologic settings, including mountain ranges, volcanic arcs, and rift zones.

In addition to its use as a decorative stone and construction material, syenite can also contain valuable minerals such as rare earth elements and is sometimes mined for these resources.

31. Teschenite

Teschenite, coarse- to fine-grained, rather dark-coloured, intrusive igneous rock that occurs in sills (tabular bodies inserted while molten between other rocks), dikes (tabular bodies injected in fissures), and irregular masses and is always altered to some extent. It consists primarily of plagioclase feldspar, analcime, and titaniferous augite, with barkevikite, nepheline, and olivine usually in lesser amounts. The plagioclase crystals often are encased in the augite to give teschenite an ophitic texture. The rock is named for its occurrence near Teschen in central Scotland it is abundant in thick sills. Teschenite grades into picrite when the olivine content increases.

58. Tachylyte

Tachylyte is a fine-grained, glassy, igneous rock that forms when basaltic lava or magma rapidly cools and solidifies. It is characterized by its high content of plagioclase feldspar and glassy texture, which gives it a dark brown to black colour. Tachylyte is often found in the margins of lava flows, dykes, and sills, where it has undergone rapid cooling due to contact with cooler rock or water. It is commonly used in the construction of high-strength concrete and as an abrasive material.

59. Tephriphonolite

Tephriphonolite is an igneous rock that contains phenocrysts of alkali feldspar, plagioclase feldspar, and pyroxene, as well as groundmass of alkali feldspar and plagioclase feldspar. It is typically a light-coloured rock that may have a fine-grained or porphyritic texture. Tephriphonolite is often associated with volcanic activity and can be found in volcanic regions around the world. It is a relatively rare rock type and is not commonly used as a building material or for other commercial purposes.

60. Tephrite

Tephrite is a type of volcanic rock that is intermediate in composition between basalt and phonolite. It is typically dark in colour and contains high levels of sodium and potassium, with lower levels of magnesium and iron. Tephrite rocks are formed from the eruption of lava that has a low viscosity, allowing it to flow easily and form relatively smooth surfaces. They are commonly found in volcanic areas such as the Canary Islands, Italy, and parts of Africa. Tephrite can also be used as a construction material and as a source of sodium and potassium for industrial purposes.

61. Tonalite

Tonalite is a type of intrusive igneous rock that is commonly found in the continental crust. It is composed of feldspar, quartz, and mafic minerals such as biotite or hornblende. The texture of tonalite is typically medium to coarse-grained, with a porphyritic texture common, featuring large crystals surrounded by smaller ones. Tonalite is similar in composition to granite but has less quartz and more plagioclase feldspar. It forms from the slow cooling of magma in the Earth’s crust and can be found in a variety of geological settings, including mountains, volcanoes, and subduction zones. Tonalite is often used as a building material and is also a source of valuable minerals such as copper and gold.

61. Trachyandesite

Trachyandesite is an igneous rock that is intermediate in composition between trachyte and andesite. It typically contains plagioclase feldspar, orthoclase feldspar, and varying amounts of biotite, hornblende, and pyroxene minerals. Trachyandesite forms from the solidification of magma that is rich in silica, alkali metals, and aluminium. It is commonly found in volcanic areas and can be used as a construction material, as well as in the manufacture of ceramics and glass.

62. Trachybasalt

Trachybasalt is a volcanic rock that is formed by the mixture of two types of magma: basaltic magma and trachytic magma. Basaltic magma is rich in iron and magnesium, while trachytic magma is rich in potassium and sodium. The combination of these two magmas results in a rock with a unique texture and mineral composition.

Trachybasalt has a dark-coloured appearance, similar to basalt, with a fine-grained texture. However, it also contains small crystals of feldspar and other minerals that are characteristic of trachyte. The exact mineral composition of trachybasalt can vary depending on the specific types of magma that mix together to form the rock.

Trachybasalt is commonly found in volcanic areas, such as the Pacific Ring of Fire. It is also used as a building material and for road construction due to its durability and resistance to weathering.

63. Trachyte

Trachyte is an igneous volcanic rock that is composed of alkali feldspars, such as orthoclase or sanidine, and lesser amounts of plagioclase, mafic minerals, and quartz. It has a fine-grained texture and can range in colour from light grey to pinkish-brown. Trachyte is typically formed through volcanic activity, and it is commonly found in areas with active or dormant volcanoes. Due to its durability and resistance to weathering, trachyte has been used as a building material for many centuries. It has been used to construct churches, castles, and other structures in various parts of the world.

64. Troctolite

Troctolite is a type of igneous rock that is composed mostly of plagioclase feldspar and olivine. It is a member of the gabbro family of rocks and is typically coarse-grained with a dark grey to black colour. Troctolite is formed from the solidification of magma deep within the Earth’s crust and is often found in association with other mafic rocks such as basalt and gabbro. The name troctolite comes from the Greek words “troktos,” meaning twisted, and “lithos,” meaning stone, referring to the twisted appearance of the olivine crystals within the rock. Troctolite has a variety of uses in construction and is also used as a source of nickel and platinum group metals.

65. Trondhjemite

Trondhjemite is a type of igneous rock that is characterized by its composition and texture. It is a granitic rock that is rich in plagioclase feldspar and quartz, with smaller amounts of other minerals such as biotite, hornblende, and pyroxene. Trondhjemite is typically light-coloured and has a fine-grained or porphyritic texture. It is named after the city of Trondheim in Norway, where it was first identified. Trondhjemite is often associated with continental crust and is thought to form through the partial melting of pre-existing rocks. It is an important rock type for understanding the evolution of the Earth’s crust and is used in a variety of scientific studies, including geochronology and geochemistry.

66. Tuff

Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into solid rock. Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous (for example, tuffaceous sandstone). Tuff composed of sandy volcanic material can be referred to as volcanic sandstone.

Tuff is a relatively soft rock, so it has been used for construction since ancient times. Because it is common in Italy, the Romans used it often for construction. The Rapa Nui people used it to make most of the moai statues on Easter Island.

Tuff can be classified as either igneous or sedimentary rock. It is usually studied in the context of igneous petrology, although it is sometimes described using sedimentological terms. Tuff is often erroneously called tufa in guidebooks and in television programmes.

34. Variolite

Variolites are mafic, igneous, and typically volcanic rocks, e.g. tholeiite, basalt or komatiite, that contain centimetre-scale spherical or globular structures, called varioles, in a fine-grained matrix. These structures are lighter coloured than the host rock and typically range in diameter from 0.05mm to over 5 cm. In 1648, Aldrovandi created the term variolite for aphanitic or fine-grained igneous rocks containing varioles. The weathering of varioles often causes variolites to have a pock-marked appearance. In allusion to the pock-marked appearance of weathered surfaces of variolite, this term is derived from the Latin word, variola, for smallpox.

67. Websterite

Websterite is a type of igneous rock that is primarily composed of clinopyroxene and plagioclase feldspar. It is named after the American geologist and lexicographer Noah Webster. Websterite is typically found in plutonic rocks, such as gabbro and norite, and can also be found in mafic and ultramafic rocks. It is commonly associated with other minerals such as olivine, hornblende, and magnetite. Websterite is commonly used in the construction industry as a decorative stone and as a source of crushed rock for road construction.

---

Inbound Links:

• List of Metamorphic Rocks
• List of Sedimentary Rocks

External Links: 

https://wikipedia.org

Uses of Igneous Rocks