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Chemical Formula | The Serpentine group is composed of several
minerals related chemically and physically. There is a
generic formula for the entire group; individual members
all fit in to the formula. The formula is: X 2-3 Si 2 O 5 (OH) 4 X = Mg, Fe2+, Fe3+, Ni , Al, Zn, or Mn. One of the two Si atoms may be replaced by an Al or Fe atom in a few rare members. This leads to a formula of (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4. The subscripted 2-3 after the first set of elements denotes that there are two or three of the selected elements, depending on the charge of the element. (Some very rare forms of Serpentine contain water [H2O] in place of the hydroxyl [OH]. Since the charge of water is different from hydroxyl, the formula of these rare forms is slightly altered.) The two most common members of the Serpentine Group are: Antigorite - (Mg,Fe)3Si2O5(OH)4 Chrysotile - Mg3Si2O5(OH)4 Chrysotile is not a single mineral, but a group of polymorphous minerals with the same chemical composition but different crystal lattice. (Chrysotile polytypes are Clinochrysotile [monoclinic], Orthochrysotile [orthorhombic], Parachrysotile [orthorhombic], and Lizardite [trigonal] ). Other members of the Serpentine group are: Amesite - Mg2Al(SiAl)O5(OH)4 Cronstedtite - Fe2+2Fe3+(SiFe3+)O5(OH)4 Fraipontite - (Zn,Al)3(Si,Al)2O5(OH)4 Nepouite - Ni3Si2O5(OH)4 There are several more rare members of the Serpentine group not discussed in this guide. |
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Composition | Basic silicate of magnesium, iron, aluminum, nickel, zinc, and manganese. (Some rare varieties contain water in place of the hydroxyl, and substitute a different metal in exchange of the charge difference.) | ||||
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Color | Yellow, green, brown, black, cream-white | ||||
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Streak | White | ||||
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Hardness | 2 - 5 | ||||
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Crystal Forms and Aggregates |
Antigorite, Clinochrysotile,
Cronstedtite, Fraipontite,
and Nepouite all crystallize in
the Monoclinic crystal system Orthochrysotile and Parachrysotile crystallize in the Orthorhombic crystal system Lizardite crystallize in the Hexagonal crystal system Amesite crystallize in the Triclinic crystal system Aggregates are massive, platy, fibrous (forming tough, flexible and elastic fibers), botryoidal, columnar, earthy, platy, micaceous, in pyramidal groupings, in parallel bladed groups, and as fibrous veins. Serpentine also pseudomorphs after several minerals, where it occurs in the same crystal shape as the pseudomorphed mineral |
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Transparency | Translucent to opaque. Rarely transparent. | ||||
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Specific Gravity | 2.5 - 3.2 | ||||
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Luster | Greasy, waxy, or silky | ||||
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Cleavage | Usually not discernible because of crystal development. Chrysotile may exhibit basal cleavage. | ||||
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Fracture | Conchoidal, splintery | ||||
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Tenacity | Brittle. Fibrous Serpentine is flexible and elastic. | ||||
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Other ID Marks | 1) Has a greasy feel 2) Yellow specimens usually fluoresce cream-white in shortwave ultraviolet light |
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Other Names |  Chrysotile Asbestos -
Synonym of Chrysotile |
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Varieties | Asbestos - Any extremely fibrous mineral. When applied to Serpentine, it
refers to the fibrous variety (Chrysotile). Chrysolite
- Describes a mineral in the Olivine Group that is often confused with Chrysotile. Serpentine forms rocks that are sometimes classified as varieties because of their almost complete Serpentine content. These are: Serpentinite, or Serpentine Rock - Rock composed almost fully of Serpentine, but contains small amounts of pyroxene and amphibole minerals, as well as Olivine, Magnetite, Calcite, and Dolomite. Verde Antique, or Serpentine Marble - Dark green rock composed of Serpentine, and containing Calcite veins. It is considered a Marble. Deweylite, or Gymnite - Chrysotile containing small amounts of Stephanite. There are numerous variety names given to different forms of Serpentine, but many of them are not officially recognized. Nevertheless, all names are mentioned here: Antigorite - An individual mineral in the Serpentine group. The term is sometimes used to describe only columnar Serpentine. Chrysotile - An individual mineral in the Serpentine group. The term is sometimes used to describe only fibrous Serpentine. Bastite - Pseudomorph of Serpentine after Enstatite. Williamsite - Translucent, light green Serpentine. Picrolite - Columnar Serpentine. Retinalite - Antigorite with a waxy luster. Marmolite - Antigorite composed of small plates. Ophiolite - Massive, mottled variety of Antigorite. Bowenite - Variety of Chrysotile that is massive shaped, and contains densely packed, colorless fibers. |
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In Group | Silicates ; Phyllosilicates | ||||
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All About | Although Serpentine is composed of several
minerals, a distinction is not usually made between
individual members. Occasionally, however, members are
individually described. Fibrous Chrysotile, a type of asbestos, should never be brought near the mouth. If its fibers or particles enter the lungs, they can cause asbestosis. Asbestosis is a lung disease caused by inhalation of asbestos particles, which causes several cancers, particularly lung cancer and mesothelioma (an inoperable cancer of the chest and abdominal lining). Symptoms of asbestosis do not arise until about 20 years after the inhalation. Washing hands after handling specimens is highly recommended. Many mineral collectors avoid collecting asbestos minerals because of the hazards. |
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Uses | The finely fibrous variety of Chrysotile is
the primary source for industrial asbestos. It produces
approximately 95 percent of all asbestos (the other 5
percent is amphibole asbestos, such as Tremolite and Actinolite). Because it is not affected by
fire and is a poor heat conductor, it is used for fire
retardant devices and heat protection. Its former use,
which has been outlawed in most areas, was as an
insulator, but has been banned because of its notorious
nature of causing cancer and other long term illnesses. Antigorite, as well as Serpentinite and Verd Antique, are often sculpted into ornamental carvings. They are soft and easy to work with, and create exceptional art. They are used as animal carvings, book ends, and the like. Carved Serpentine, Serpentinite, and Verd Antique are only used as indoor ornaments, since rain removes the polish. |
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Striking Features | Greasy feel, soft compared to similar minerals, and may flexible and elastic. | ||||
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Popularity (1-4) | 2 | ||||
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Prevalence (1-3) | 1 | ||||
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Demand (1-3) | 1 | ||||
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Distinguishing Similar Minerals |
Talc - softer (1) Chlorite - softer (2 - 2½) Tremolite and Actinolite Asbestos - harder (5 - 6), less flexible Nephrite - harder, less greasy |
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Commonly Occurs With |
Talc, Magnetite, Dolomite, Artinite, Olivine, Calcite, Magnesite. Amesite occurs with Diaspore. |
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Noteworthy Localities |
Serpentine is a very common mineral, and is
found worldwide. Some famous localities include The
Lizard, Cornwall, England; the Antigorio Valley,
Piedmont, Italy; and Mount Olympus, Cyprus. The Jeffery
Asbestos Mine in Richmond Co., Quebec, is the most
productive asbestos mine providing great amounts of
Chrysotile as well as many other minerals. Thetford, in
Megantic Co., Quebec has produced fine Chrysotile
specimens. In the U.S., large amounts of Serpentine were
found in Montville, Morris Co., and Hoboken, Hudson Co.,
New Jersey; Fresno, Calaveras, San Benito, Mariposa, and
Toulumne Cos., California; and Gila Co., Arizona. In the
Tilly Foster Mine, Brewster, Putnam Co., New York, many
minerals have been replaced by Serpentine, and large
amounts of Serpentine were found there. Other occurrences
were at Newburyport, Essex Co., Massachusetts; Antwerp,
Gouverneur, and Balmat; St. Lawrence Co., New York; and
Staten Island (Richmond Co.), New York. Other Serpentine varieties Amesite is found in Chester, Hampden Co., Massachussetts, associated with Diaspore. It also occurs in Dufek massif, in the Pensacola Mountains, Antarctica. Cronstedtite is found in Pribam and Kuttenberg, Bohemia, Czech Republic. It also occurs in Wheal Maudin and Wheal Jane, Cornwall, England, and in Congonhas de Campo, Minas Gerais, Brazil. Fraipontite is found in Vielle-Montague, Belgium and in the Silver Bell mine, Gleeson, Cochise Co., Arizona. It is usually an alteration product of Smithsonite. Nepouite is found in the Nepoui Mine in New Caledonia. It is also found in the 132 North nickel mine, Widgiemooltha, Western Australia and in Letovice, Czech Republic. Nepouite is an important ore of nickel. It is often called Garnierite, but that is not its proper scientific name. |
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Picture Icon Links |
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Picture Links | 1. Vein of
Serpentine (Chrysotile) in rock 2. Chunk of a Serpentine (Chrysotile - variety Picrolite) vein |
