Miscellaneous Ores

(1). Chromite: Fe2+Cr2O4

Physical Properties of Chromite:

  • Crystal Systems: Cubic
  • Cleavage: Absent
  • Fracture: uneven
  • Hardness: 5.5 on Moh’s scale
  • Sp.Gr: 4.6
  • Lustre of Chromite: Submetallic
  • Colour: Black
  • Streak: Dark Brown
  • Habit: commonly massive or granular

Occurrence: Chromite occurs in igneous rocks such as peridotites and other ultrabasic rocks and in serpentine derived from them. It is also found in alluvial deposits.

Uses of Chromite:

  • Chromite is used as a refractory material.
  • Chromite is used as an ore of chromium, which is used to harden the steel, chrome plating, and alloying for the production of super-alloys (corrosion-resistant alloys).
  • Chromium is also used in alloys to make them chemical resistant.

(2). Ilmenite: FeTiO3

Physical Properties of Ilmenite:

  • Crystal system of Ilmenite: hexagonal
  • Cleavage of Ilmenite: cleavage is absent
  • Fracture: conchoidal
  • Hardness on Moh’s scale: 5.5 – 6
  • Sp.gr: 4.7
  • Lustre: metallic to dull
  • Colour: iron-black
  • Streak: Black
  • Habit: thick tabular crystals, often massive or as sand grains.

Occurrence: Ilmenite occurs as an accessory mineral in igneous rocks such as gabbros, diorites, and anothosites. It is also found in ore veins and pegmatites. Beach sands may also contain ilmenite.

Uses of Ilmenite:

  • Ilmenite is used as an ore of titanium, which is a hard metal resistant to corrosion.
  • Titanium is resistant to heat and corrsion, therefore, the fans of aircraft are made with titanium.

(3). Monazite: (Ce,La,Nd,Th)(PO4,SiO4)

Physical properties of Monazite: 

  • Crystal System: Monoclinic
  • Cleavage: Poor
  • Fracture: uneven
  • Hardness: 5 – 5.5
  • Sp.Gr: 4.6 – 5.4
  • Lustre: Resinous
  • Colour: yellowish-brown, or reddish-brown
  • Streak: White
  • Habit: Monazite is habited as granular masses and as sand.

Occurrence: Monazite occurs as an accessory mineral in granites and gneisses. It gets concentrated in alluvial sands which are the chief source.

Uses:

  • Monazite is a principal source of thorium, cerium, and other rare earth elements.
  • The rare earth elements have high electrical conductivity.
  • Monazite is a major source of radioactive elements.

(4). Barytes: BaSO4

Physical Properties of Barytes:

  • Crystal System: monoclinic
  • Cleavage: poor
  • Fracture: uneven
  • Hardness: 3 -3.5
  • Sp.Gr: 4.5 on Moh’s scale
  • Lustre: Vitreous
  • Colour: colourless, white, yellow, gray, pale-green, red and brown.
  • Streak: white
  • Habit: Baryte is usually habited in tabular, fibrous, lamellar and granular.

Occurrence: Barytes commonly occurs as a gangue mineral in metalliferous hydrothermal veins. In seddimentary rocks, it occurs as veins and concretions.

Uses of Baryte: 

  • Baryte is mainly used as a weight agent in drilling mud for oil and gas wells.
  • Baryte is also used for making paints.
  • Baryte is used as an aggregate in manufacturing heavy cement.
  • It is used in industries for the production of barium chemicals.
  • Radioactive material barium can also be extracted from Baryte.
  • Used as filler and extender.

(5). Magnesite: MgCO3:

Physical Properties: 

  • Crystal System: hexagonal
  • Cleavage: perfect
  • Fracture: conchoidal or uneven
  • Hardness: 3.2 on Moh’s scale
  • Sp.Gr: 3.0 -3.2
  • Lustre: vitreous or earthy
  • Colours: white, colourless, gray, brown or yellow
  • Streak: white
  • Habit: Usually massive, fibrous, or granular

Occurrence: Magnesite is formed by the replacement of limestone by the solution containing magnesium. It is also formed by the action of carbonate-rich solution on rocks containing magnesium minerals.

Uses of Magnesite:

  • Magnesite is used to produce magnesium oxide (MgO), which is used as refractory material for steel industry.
  • MgO is also used as a raw material for chemical industry.
  • Magnesite is also used in making cement, refractory bricks, and crucible.

(6). Molybdenite: MoS2

Physical properties of Molybnite:

  • Crystal System of Molybdenite: hexagonal
  • Cleavage of Molybdenite: perfect
  • Hardness on Moh’s scale: 1- 1.5
  • Sp. Gr: 4.7
  • Lustre: Metallic
  • Colour: lead grey
  • Streak: greenish grey
  • Habit: Molybdenite is habited in tabular, foliated crystals, or maybe found in massive form.

Occurrence: In small amounts, it occurs in granites and pegmatites. It also occurs in deep-seated hydrothermal veins, where it is associated with scheelite, wolframite, topaz and flourite.

Uses of Molybdenite:

  • Molybdenite is used as an ore of Molybdenum, which is widely used as an ingredient in steel. Small amounts of molybdenum added to steel and other alloys can significantly increase their toughness, heat resistance, hardness, strength, and resistance to corrosion.
  • Molybdenum element is also used in fertilizer, as a catalyst, and in battery electrodes.

(7). Cinnabar: HgS

Physical Properties:

  • Crystal System: hexagonal
  • Cleavage: perfect
  • Hardness: 2 – 2.5
  • Specific gravity of cinnabar: 8.9
  • Lustre: crystals have adamentine, massive varieties have a dull lustre.
  • Colour: Scarlet, brownish red
  • Streak: red
  • Habit: Crystals rhombohedral or tabular. Also granular and massive.

Occurrence of Cinnabar: Cinnabar is a low-temperature mineral, which is found in hydrothermal deposits in volcanic regions. It is also deposited in hot springs. Cinnabar is found associated with pyrite, chalcopyrite, realgar and stibnite.

Uses of Cinnabar: 

  • Cinnabar is a chief ore of mercury.
  • Cinnabar is used as red colour in paints and tatoo dyes.
  • According to the traditional Chinese medication, a minor quantity of cinnabar is added to about 40 varieties of medicines.

(8). Arsenopyrite: FeAsS

Physical properties of Arsenopyrite:

  • Crystal system of Arsenopyrite: Monoclinic
  • Cleavage: poor
  • Fracture: uneven
  • Hardness: 5.5 – 6.0 as per Moh’s scale
  • Sp.gr. of Arsenopyrite: 5.9 – 6.2
  • Lustre: Metallic
  • Colours of Arsenopyrite: Silver-white to Grey-white
  • Streak: Greyish black
  • Habit: Prismatic crystals with striations. Also massive or granular.

Occurrence: Arsenopyrite is the most abundant arsenic mineral. it occurs with tin and tungsten ores in high-temperature hydrothermal deposits.

Uses of Arsenopyrite: 

  • Arsenopyrite is the chief source of arsenic element.
  • By smelting arsenopyrite, we can produce arsenic trioxide (As2O3), which is used as an herbicide, insecticide, pesticide, and in making chemical weapons.
  • Arsenopyrite is used during firework to add colour to the glass and metallic instruments.
  • Arsenic compounds are also used in medicines, to add the effectiveness of antibiotics.
  • Arsenic is used as a colour pigment in paints.

(9). Orpiment: As2S3

Physical Properties of Orpiment:

  • Crystal System: Monoclinic
  • Cleavage: Perfect
  • Hardness: 2 as per Moh’s scale
  • Specific gravity: 4.52 -4.62
  • Lustre: Metallic
  • Colour: Lead grey
  • Streak: Lead grey
  • Habit: Often in radiating crystal groups.

Occurrence: Stibnite is found in low-temperature hydrothermal veins or replacement deposits and in hot springs deposits. It is usually associated with realgar, galena, pyrite, and cinnabar.

Uses of Orpiment: 

  • Orpiment is used as an ore of Antimony.
  • It is also used in the production of infrared-transmitting glass, oilcloth, linoleum, semiconductors, photoconductors, pigments, and fireworks.
  • In many rural areas of South Asia Orpiment is mixed with slaked lime (1:2 ratio) to make hair removing agent (depilatory).

(10). Wolframite: (Fe, Mn) WO4

Physical Properties of Wolframite: 

  • Crystal System: Monoclinic
  • Cleavage: Perfect
  • Fracture: Uneven
  • Hardness: 4- 4.5
  • Sp.Gr: 7.25- 7.60
  • Lustre: resinous, metallic or submetallic.
  • Colours: Reddish-brown to Brownish-black
  • Streak: Reddish-brown to Brownish-black
  • Habit: Short prismatic crystals, often massive

Occurrence: Wolframite occurs in quartz veins and pegmatites. In granites, it is found associated with cassiterite, scheelite, etc. It also occurs in some alluvial deposits where it has been concentrated by water action.

Uses of Wolframite: 

  • It is a chief ore of tungsten. Tungsten is a strong and quite dense material with a high melting temperature used for electric filaments and armour-piercing ammunition, as well as hard tungsten carbide machine tools.
  • Tungsten is essentially used for the production of ballistic missiles and drills.

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