The best known color of precious gemstone epidote is “pistachio” green, and this massive mineral is also called pistacite, in reference to its color. The crystal system is monoclinic and its habit is long prismatic, often striated vertically. Precious gemstone epidote has a 0.030 dispersion and 3.4 specific gravity. The name epidote is from the Greek epidosis, meaning “adittion” or “increase,” which is believed to refer to the fact that some of the crystals faces of this mineral are longer than others. Precious gemstone epidote is famously known from Green Monster Mountain in Alaska, and also from India, Sri Lanka, and Brazil. Others sources are in India, Myanmar, Switzerland, Madagascar, Austria, Norway, and Pakistan. The chrome green variety of precious gemstone epidote is known as tawmawite, in which up to 11 percent of the aluminum in its formula is replaced by chromium.
With an even fracture and 6.5 hardness level, Precious gemstone epidote is a very common mineral, but a rare collector’s gem. Coming from the class of silicates with silica tetrahedra in pairs, it is composed from calcium iron aluminum silicate hydroxite. Precious gemstone epidote is available in a color of brownish green, yellow green, rich chrome green, black, and dark green. Despite its hardness and deep color, precious gemstone epidote is not commonly cut and polished as a precious gem because the large crystals are rarely clear enough to facet. For gem material, the refractive index is 1.736-1.770 and its birefringence is 0.34. Cushion and step cut are the most common faceted cuts. The luster of precious gemstone epidote is vitreous and its cleavage is perfect in one direction.
Natural gemstones like precious gemstone epidote is the chief member of a silicate mineral group, which normally occur in low-grade, calcareous metamorphic rocks and also in igneous rocks, where they have altered from feldspar, pyroxene, and amphibole minerals. As a calcium aluminosilicate, precious gemstone epidote forms pistachio-green fibrous or granular masses, disseminated grains, or dark green elongated crystals, which have perfect cleavage in one direction. With both single and double silicate tetrahedral groups, epidote is a structurally complex mineral. There is a strong pleochroism, showing yellow, green, and brown, depending on direction. Precious gemstone epidote often forms inclusions in quartz.
Saturday, May 14, 2011
Wednesday, May 11, 2011
Natural Crystal Enstatite
The name natural crystal enstatite is derived from the Greek word enstates, meaning “opponent,” which refers to the gem’s reluctance to be melted by a blowpipe, an early method for determining mineral chemistry. It was first described by German geologist G.A. Kenngott in 1855. Like hypersthene, it is a member of the pyroxene family of minerals, natural crystal enstatite is a magnesium silicate with 1.650-1.673 refractive index. Natural crystal enstatite is from single-chain silicates class with orthorhombic crystal system. Available colors are in white, green, brown, grey, or colorless
With dispersion range between 0.019-0.022 and birefringence between 0.009-0.010, natural crystal enstatite is not well known in the world of natural gemstones and is mainly a collector’s item. The habit is prismatic, layered, and massive. However, it can be found in jewelry as a cat’s eye (cut en cabochon) or faceted in a step cut, usually in pendants or earrings. It is too soft for rings. Natural crystal enstatite crystals with a clear crystal shape are the rarest, and therefore the most valuable. Its luster is vitreous to pearly and the fracture is conchoidal.
Natural crystal enstatite is most often found in metamorphic or igneous rocks and has also been discovered in some meteorites. It forms in the orthorhombic crystal system but its structure changes to a monoclinic symmetry structure (known as clinonatural crystal enstatite) at very high temperatures. The hardness stopped at 5.5 Mohs. Natural crystal enstatite has distinct-in-two-directions cleavage and specific gravity in 3.22-3.28 interval. Bright green natural crystal enstatite (whose color is due to traces of chromium) occurs in South Africa and is known as chrome natural crystal enstatite, which is cut as a gemstone. Greenish brown stones are found in upper Burma (Myanmar), and these exquisite stones often show an excellent cat’s eye effect, with a thin orange to pale brown line on an almost black background. Some colorless stones and grayish cat’s eye specimens are found in Sri Lanka. A deep brown, six-rayed star natural crystal enstatite has been seen in Mysore, India. Natural crystal enstatite is also available in Tanzania, Kenya, Germany, Greenland, and Norway.
With dispersion range between 0.019-0.022 and birefringence between 0.009-0.010, natural crystal enstatite is not well known in the world of natural gemstones and is mainly a collector’s item. The habit is prismatic, layered, and massive. However, it can be found in jewelry as a cat’s eye (cut en cabochon) or faceted in a step cut, usually in pendants or earrings. It is too soft for rings. Natural crystal enstatite crystals with a clear crystal shape are the rarest, and therefore the most valuable. Its luster is vitreous to pearly and the fracture is conchoidal.
Natural crystal enstatite is most often found in metamorphic or igneous rocks and has also been discovered in some meteorites. It forms in the orthorhombic crystal system but its structure changes to a monoclinic symmetry structure (known as clinonatural crystal enstatite) at very high temperatures. The hardness stopped at 5.5 Mohs. Natural crystal enstatite has distinct-in-two-directions cleavage and specific gravity in 3.22-3.28 interval. Bright green natural crystal enstatite (whose color is due to traces of chromium) occurs in South Africa and is known as chrome natural crystal enstatite, which is cut as a gemstone. Greenish brown stones are found in upper Burma (Myanmar), and these exquisite stones often show an excellent cat’s eye effect, with a thin orange to pale brown line on an almost black background. Some colorless stones and grayish cat’s eye specimens are found in Sri Lanka. A deep brown, six-rayed star natural crystal enstatite has been seen in Mysore, India. Natural crystal enstatite is also available in Tanzania, Kenya, Germany, Greenland, and Norway.
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