The olive green colour and scaly or smooth appearance is mainly the basis behind the name serpentines, which means "serpent rock". They actually have their origin in metamorphic alteration of pyroxene and peridotite. Serpentines may also pseudomorphously replace other magnesium silicates. These alterations may be incomplete leading to variation of physical properties of Serpentine. Antigotite is polymorph of serpentine that commonly forms during metamorphism of wet ultramafic rocks and is also stable at highest temperatures. On the contrary, the chrysotile and lizardite typically forms near the Earth surface and also breaks down at comparatively low temperature, may be below 400 degree Celsius. It has been suggested that chrysotile is never stable relative to either of the other two serpentine polymorphs. Most of the serpentines are translucent or opaque, susceptible and infusible to acids. All are massive and microcrystalline in habit, never being found as single crystals. Luster or shine may be greasy, vitreous or silky. The colour of the gemstone vary from grey to white, green to yellow, black to brown, and are often veined or splotchy. And there are also many which inter-grow with other minerals like dolomite and calcite. When rocks are composed of these minerals then it is called serpentinite. There are many benefits of serpentine and they find application in industrial usage and in many other purposes as well like railway ballasts, building materials and asbestos form type find use as electrical and thermal insulation. There are many varieties of serpentines that are available and most durable and attractive varieties are termed as "precious" or "noble" serpentine and are extensively used as gems in ornamental carvings. When they are dyed they may also imitate jade. |