Serpentine

Serpentine is not a single mineral but a group of three main minerals with nearly the same chemical composition but different structures: antigorite, lizardite and fibrous chrysotile. It is usually green, slippery and soft; its name comes from the Latin serpentinus, “snake-like”, because its surface resembles snakeskin. These are the main minerals of the rock serpentinite. Some kinds are used as ornamental stone and as a jade imitation; the fibrous chrysotile kind is asbestos.

Ornamental and carving stone: Bowenite is the serpentine most often met in carving and jewellery. “Verde antico”, a brecciated serpentinite quarried in classical times at Casambala in Thessaly, Greece, was sought after as a facing stone. Historical use: It was a material for the cylinder seals of ancient Mesopotamia. Raw material: Serpentine rock is used as railway ballast and building material; it is a source of magnesium and of asbestos (use of which is now banned in many countries).

It has a hardness of 2.5–4 on the Mohs scale. A fingernail cannot scratch it, but a steel knife can. Its specific gravity is 2.5–2.6 g/cm³.

Its best-known localities: Kennack Cove, The Lizard, Cornwall, England; Val Antigorio, Piedmont, Italy; Unst, Shetland Islands, Scotland; Connemara, County Galway, Ireland; Xiuyan, Liaoning, China.

Green (in yellowish, bluish, greyish or blackish tones), with a waxy, greasy or silky lustre; it feels slippery. Most kinds are soft (hardness 2.5–4): a steel knife scratches them; hard, translucent kinds such as bowenite reach 5.5. The three main minerals can be roughly told apart like this: lizardite is fine-grained and waxy; antigorite is platy or bladed, sometimes fibrous; chrysotile is silky, flexible fibres. X-ray diffraction or a microscope is needed for certain identification. Bowenite, a light apple-green, fine-grained hard serpentine, looks like jade; it was also known by the Persian name sang-i-yashm, “false jade”. It is softer than true jade (nephrite, jadeite), with a hardness of about 5.5.

On the “street to diamond” value ladder it sits on step 3 of nine: Building and industrial stone. The value of serpentine varies with its kind and use. As an ornamental stone, colour (especially a vivid, jade-like green), translucency, beauty of pattern and quality of polish are decisive; hard, translucent kinds such as bowenite are more sought after, while soft kinds carve easily but scratch easily. Pieces containing fibrous chrysotile (asbestos) are worthless because of the health risk, and working them is hazardous.

Today crystal-therapy sources present serpentine as a “stone of balance”, claiming that it opens the heart chakra, soothes the nervous system and reduces stress and tension. The same sources claim that serpentine helps with kidney, liver and spleen complaints and strengthens the immune system. No study shows that serpentine helps the organs or the immune system. On the contrary, serpentine rocks may contain veins of fibrous chrysotile (asbestos): the dust of these stones should not be inhaled, and no stone water or elixir should be made from them. For stress, tension or organ complaints, seek medical support. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.

The fibrous member of the serpentine group, chrysotile, is, like all types of asbestos, carcinogenic to humans (IARC Group 1). Because serpentine rocks can contain veins of chrysotile, the dust released in cutting, sanding or grinding serpentine stone should not be inhaled; when serpentine rock is used for road surfacing, asbestos fibres can also become airborne. Serpentine powder should not be swallowed and no stone water or elixir should be made from it. Do not break specimens that look fibrous or have silky veins. In Türkiye the production, placing on the market and use of asbestos and asbestos-containing products has been banned since 31 December 2010.