Minerals of Serpentine Group

Surpentinite rock containing surpentine mineral

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.

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