Serpentine is said to owe its name either to its serpent-like colours and patterns or from an old belief that the stones were effective protection from snake bites. They have their origins in metamorphic alterations of peridotite, amphibolite and pyroxene. Serpentines may also pseudomorphously replace other magnesium silicates. Alterations may be incomplete, causing physical properties of serpentines to vary widely. Where they form a significant part of the land surface, the soil is unusually high in clay.
Soils derived from serpentine are toxic to many plants due to their high mineral content, and the flora is generally very distinctive, with specialised, slow-growing species. Areas of serpentine-derived soil will show as strips of shrubland and open, scattered small trees (often conifers) within otherwise forested areas.
Most serpentines are opaque to translucent, light (specific gravity between 2.2-2.9), soft (hardness 2.5-4), infusible and susceptible to acids. All are microcrystalline and massive in habit, never being found as single crystals. Lustre may be vitreous, greasy or silky. Colours range from white to grey, yellow to green, and brown to black, and are often splotchy or veined. Many are intergrown with other minerals, such as calcite and dolomite. Occurrence is worldwide; New Caledonia, Canada (Quebec), USA (northern California), Afghanistan, Cornwall, China, France, Norway and Italy are notable localities.
Rock composed primarily of these minerals is called serpentinite. Serpentines find use in industry for a number of purposes, such as railway ballasts, building materials, and the asbestiform types find use as thermal and electrical insulation (chrysotile asbestos). The more attractive and durable varieties (all of antigorite) are termed “noble” or “precious” serpentine and are used extensively as gems and in ornamental carvings. Often dyed, they may imitate jade. Misleading synonyms for this material include “Korean jade”, “Suzhou jade”, “Styrian jade”, and “New jade”. New Caledonian serpentine is particularly rich in nickel, and is the source of most of the world’s nickel ore.
The Māori of New Zealand once carved beautiful objects from local serpentine, which they called tangiwai, meaning “tears”.
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