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| Narsarsukite from Kola Peninsula |
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More Narsarsukite on ebay auction |
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Narsarsukite - http://www.galleries.com/minerals/silicate/narsarsu/narsarsu.htm Narsarsukite is not a well known mineral, but it is a nice collection mineral. It is named for the wonderful mineral locality at Narsarsuk, Greenland, from where the first specimens were described in 1900. The locality is the result of agpaitic pegmatite intrusions, an unusual igneous rock that is high in alkaline metals (such as sodium) and poor in silica. These intrusions also contain a large number of unusual elements such as titanium, fluorine and rare earth metals. Narsarsukite is also found at Mont Saint-Hilaire, Quebec; another agpaitic pegmatite location. Here is probably the best location for narsarsukite specimens as crystals are relatively large and well formed. Narsarsukite has been cut as a gemstone, although do not expect to see it available in many jewelry stores. It is cut mostly for gemstone collectors, but is considered attractive. A cut stone of 0.31 carats was cut from the mines of Mont Saint-Hilaire, Quebec and is the largest known narsarsukite gemstone. Narsarsukite's structure involves double chains of linked silicate tetrahedrons in a tube like arrangement. The chains are actually kinked into a what is best described as a "crankshaft" shape with the kinks going up and down like a crankshaft. The chemistry of narsarsukite may include yttrium, calcium and potassium, but they are not usually significant enough to include in the general formula. www.gemstone.org The different shades of colour have been assigned different names in the trade. For example, deep red Tourmaline is named "Rubellite”, provided it shows the same fine ruby-red shade in daylight and in artificial light. Should the colour change when the source of light changes, the stone will be called a "Pink Tourmaline”. Blue Tourmalines are called "Indigolith”, "Dravite” is a golden-brown to dark brown Tourmaline, and black Tourmalines are known as "Schorl”. The latter stone is mainly used for engravings and in esotericism, where it is highly cherished because it is reputed to ward off harmful radiation from its wearer.... www.mineralminers.com Class: cyclosilicates Crystal system: hexagonal-rhombohedral; 3m Crystal habit: commonly forms prismatic crystals with well developed trigonal prism and second-order hexagonal prism faces, can be elongated or flattened, commonly vertically striated. In cross section the prism faces often round into one another giving the appearance of a spherical triangle. Doubly terminated crystals often show different forms at each end of the vertical axis. Also radiating, acicular, columnar, massive. Twinning: very rare and simple on pyramidal planes such as {1011} Specific gravity: 2.96 - 3.31 (buergerite 3.31, dravite 3.03-3.15, elbaite 3.03-3.10, liddicoatite 3.02-3.08, schorl 3.10-3.25 and uvite 2.96-3.06) Index of refraction: 1.610-1.735 (buergerite 1.655-1.735, dravite 1.610-1.661, elbaite 1.615-1.655, liddicoatite 1.621-1.637, schorl 1.625-1.675 and uvite 1.612-1.638) Birefringence: 0.016-0.080 (buergerite 0.080, dravite 0.021-0.026, elbaite 0.016-0.024, liddicoatite 0.016,schorl 0.025- 0.035 and uvite 0.017-0.020) Pleochroism: strong in all species Hardness: 7.0 - 7.5 Color: tourmalines occur in all colors. Buergerite is dark brown to black. Dravite is usually brown to black, can be colorless. Elbaite and liddicoatite occur in a wide range of colors and shades including green, yellow, blue, pink to red, colorless and brown. Schorl is usually black, dark blue or dark blue-green. Uvite is usually black, brown or green. Tourmaline crystals are often color zoned concentrically and/or along the C axis. Luster: vitreous to resinous, can occur with chatoyancy due to tubular cavities parallel to the C axis. Transparency: transparent to opaque Cleavage: poor in all species except buergerite which has distinct prismatic cleavage Fracture: conchoidal, brittle Streak: white |
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