Thursday, 8 August 2013

Serpentine Group of Gemstone

Green Serpentine
Hydrated silicate of magnesium. Serpentine can contain three polymorphs: lizardite, chrysotile and antigorite. Al least two of the three are usually present. Gemologists recognize serpentine as a species. Mineralogists recognize it as a group name, geologists as the 'rock type serpentinite. It is so named because of its resemblance to the reticulations of snakeskin.

Crystal system

Orthorhombic for lizardite; monoclinic for antigoritn and chrysolite.

Appearance

Minorala of the serpentine group occur In mIcrocrystalline veins (more rarely, MRS808) of transketunt, waxy appearance, of n greenish gray to grayish white, or green color, in dark green or blackish colored rocks, I.e. ncirpontinites.

Physical properties

The densities within the group vary from 2.3-2.6. The hardness also varies from 2-3, but serpentinite itself can be as hard as 5. As is often the case with microcrystalline materials, only one refractive index can normally be established; it is usually about 1.55-1.56.

Genesis

It is a product of regional metamorphism, in a strongly aqueous environment, of magnesium-rich minerals olivine, but MAO pyroxenes and amphiboles.
                                                                    

Occurrence

It Is a very nommen mineral.

Serpentine

The massive varieties of serpentinite are particularly appreciated by gemologists when they have a definite, pleasing color, and are then called simply serpentine or maybe "serpentine jade." The term jade is a misnomer, but it is understandable because, as in the case of jadeite jade and nephrite jade, it relates to the uses made of these materials as a result of certain properties they possess, rather than to their mineralogical status.

Appearance

SerpentineIt is translucent, waxy, usually greenish white to soft pale green. Sometimes, groups or rows of small, striking, whitish cloud shapes are visible on the in-side. The yellow-green to definite green varieties are less common. Multicolored pieces are also found, with light green to green, yellow-green, or brown patches. Serpentine is mainly used for the carved figurines or decorated vases up to eight to twelve inches high, typical of Chinese art. Being fairly tenacious (although less so than jade), it is suitable for the fashioning of the classic vases with hanging chains carved from a single piece of stone. Very elaborate compositions are often found as well, such as leafy branches, groups of birds, and flowering shrubs. Skillful use of different patches of color increases the value of such pieces. But serpentine is used still more often for the large-scale production of low quality items, because ii is less costly than true jade and easier to work, being less hard. Typical of this type of work are small elephants or oriental divinities. The less common, green, yellow-green or yellow varieties are also rounded, polished and made into beads for necklaces and bracelets.

Distinctive features

Serpentine lionWhen the color is greenish white, with a waxy translucence and the characteristic white cloud formations just below the surface, it is easily recognizable at first sight. It differs from jadeite jade in having a lower density and hardness. It is mainly distinguished from nephrite jade, which is normally a bit less translucent and less waxy, by its density, while the difference in hardness is less clear (the serpentine used for ornamental purposes has a hardness range of 4.5 to 5. Occurrence Most serpentine used for ornamental purposes comes from England, New Zealand, Korea, China, and the United States.

Value

Its value is slightly lower than that elnephrite lade. ia therefore quite high for finely cralmil obmeta, pouululy fashioned from multicolored pieces, tail diglinelly low tor mem-I-produced Items. Simulants and synthetics Oriental-style figurines have been produced from a light green, translucent, waxy-looking plastic. These are highly deceptive at first sight, looking very much like serpentine. Their density is much lower. but it is not always easy to detect without proper measurement. Serpentine has not been produced synthetically.

Writer – Curzio Cipriani & Alessandro Borelli

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