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Rarely, it can be found as neon green or electric blue. Tourmaline ( / ˈtʊərməlɪn, - ˌliːn / TOOR-mə-lin, -leen) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a wide variety of colors.
Pleochroism is an extremely useful tool in mineralogy and gemology for mineral and gem identification, since the number of colors visible from different angles can identify the possible crystalline structure of a gemstone or mineral and therefore help to classify it. Minerals that are otherwise very similar often have very different pleochroic ...
References. [ 1][ 2] Carnelian (also spelled cornelian) [ 3] is a brownish-red mineral commonly used as a semiprecious stone. Similar to carnelian is sard, which is generally harder and darker; the difference is not rigidly defined, and the two names are often used interchangeably. Both carnelian and sard are varieties of the silica mineral ...
Povondraite is a rare silicate mineral from the tourmaline group with formula: NaFe 3+3 (Fe 3+4 ,Mg 2 ) (BO 3) 3 Si 6 O 18 (OH) 3 O. [2] It is a dark brown to black nearly opaque mineral with a resinous to splendent luster. It crystallizes in the trigonal crystal system as equant, distorted prisms with trigonal pyramid terminations.
Ebony. Cross-section of an unprocessed piece of ebony wood. Ebony is a dense black/brown hardwood, coming from several species in the genus Diospyros, which also includes the persimmon tree. A few Diospyros species, such as macassar and mun ebony, are dense enough to sink in water. Ebony is finely textured and has a mirror finish when polished ...
Acacia melanoxylon is able to grow to a height of around 20 m (66 ft) and has a bole that is approximately 150 cm (59 in) in diameter. It has deeply fissured, dark-grey to black coloured bark that appears quite scaly on older trees. It has angular and ribbed branches. The bark on older trunks is dark greyish-black in colour, deeply fissured and ...
Fluor-buergerite, [5] originally named buergerite, is a mineral species belonging to the tourmaline group. It was first described for an occurrence in rhyolitic cavities near Mexquitic, San Luis Potosi, Mexico. It was approved as a mineral in 1966 by the IMA and named in honor of Martin J. Buerger (1903–1986), professor of mineralogy at the ...
Cassiterite. Pleochroic haloes have been observed. Dichroic in yellow, green, red, brown, usually weak, or absent, but strong at times. Cassiterite is a tin oxide mineral, SnO 2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem.
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