Minerals of Serpentine Group

The word serpentine has been derived from ”Serpent”, which means greenish. Serpentines are so called because of their green colors. Serpentine occurs in two distinct forms: (i) ”Antigorite”; a platy variety, and (ii) ”Chrysolite; a fibrous variety.

Minerals species of Serpentine Group:

• Amesite: Chemical composition of Amesite is Mg₂Al₂SiO₅(OH)₄., however if an Amesite has Ni instead of Mg, it will be included in the Ni-Serpentine subgroup.
• Antigorite: Antigorite is a platy variety of serpentine minerals.
• Cronstedtite: It is a complex iron silicate mineral belonging to the serpentine group of minerals. Its chemical formula is Fe ²⁺ 2Fe ³⁺ (Si,Fe ³⁺. O 5)(OH) 4.
• Chrysotile: The fibrous form of serpentine group, which is used as a source of asbestos. Asbestos are used as fire-proofing and insulatory material in the buildings.
• Guidottiite: it is black in colour. Its is enriched with Manganese instead of Magnesium. Its chemical formula is Mn2Fe3+(SiFe3+)O5(OH)4. It is the first mineral of serpentine group discovered manganese constituent.
• Lizardite: It belongs to Jade Serpentine Group, which is used in carving.

Varieties of Serpentine Subgroup:

Bastite	Name for pseudomorphs of serpentine-group minerals after enstatite.
Marmolite	Light green pearly serpentine, which may show a somewhat laminated fracture pattern.
Metaxite (of de Fourestier)	Variously described as a variety of antigorite or chrysotile.
Ni-Serpentine	A name for artificial serpentine-group minerals with Ni replacing Mg. Essentially Ni-rich antigorite or amesite.
Nickeliferous Serpentine	A nickel-bearing variety of serpentine.
Pelhamine
Picrolite	Columnar or coarsely fibrous (non-asbestiform) variety of serpentine, commonly referred to as a variety of antigorite but may be other species.
Radiotine	A name for serpentine occurring in spherical aggregates of radiating fibers.
Retinalite	Honey-yellow to light green, massive, sometimes gem-quality, serpentine.
Ricolite	A variety of serpentine interbanded with talc.
Serpentinasbest	Asbestiform varieties of “serpentine”, i.e., members of the serpentine group (usually chrysotile).
Serpentine Jade	A dense cryptocristalline mixture of serpentine group minerals, mainly antigorite, chrysotile and lizardite, which is used for carving. It also contains a variety of minor impurities such as chlorite, ilmenite, magnetite and talc. Technically, this materi…

 

Antigorite and Chrysotile: (Mg,Fe²⁺)₃Si₂O₅(OH)₄

Physical properties: 

• Crystal System: Minerals of the Serpentine group have a monoclinic crystal system.
• Cleavage: Though they are found in platy and fibrous form, therefore the platy variety has a good basal cleavage, while the fibrous variety has not cleavage.
• Hardness: Mineral of the serpentine group have a variable hardness between 4-4 as per Moh’s scale.
• Sp.Gr: The minerals have low specific gravity i.e. 2.5-2.6.
• Lustre: The fibrous variety of serpentine has silky lustre, while the massive/platy forms have greasy lustre.
• Colours: The minerals of Serpentine have green and brown colours with various shades.
• Habit: Lamellar, platy/massive, and fibrous habits. Chrysotile variety has a fibrous habit.

Occurrence of Serpentine Minerals:

Serpentine is usually formed by the alteration of magnesium silicates such as olivine, pyroxene, and amphibole. It is found associated with magnesite, chromite, and magnetite. Serpentine is a rock, which is made up mostly of the variety antigorite. It is formed by the alteration of olivine-bearing rocks.

Uses of Serpentine:

• The chrysotile variety of serpentine is the chief source of asbestos. Asbestos products are used for fire-proofing and as an insulation material against heat and electricity.
• Serpentines are used as a major source of magnesium.
• Serpentines are also used as decorative stones in the building.
• Guidottiite is a member of the Serpentine group, which is used in cosmetics to add “shimmer” or “frost.”
• Ricolite is used as an architectural material and ornamental stone and for decorative purposes.

Also read:

• Minerals of Chlorite Group
• Minerals of Garnet Group
• Minerals of Olivine Group
• Minerals of Mica Group