The spinel

Name of spinel derives from the Latin "little thorn" in connection with the form of crystals, or from the Latin "thorn" as coloration of some species like the color of the berry bramble. Spinel was first described in 1546. The dimension of the crystals are usually small, but sometimes there are more than a foot in length, weighing about pounds (Southern Urals, North America). The hardness on the Mohs scale is 8.

Name of spinel derives from the Latin little thorn in connection with the form of crystals

Fig.1. Spinel (transparent crystal noble spinel (Burma)).

The chemical composition of the spinel - magnesium aluminate MgAl2O4, with part of magnesium is often replaced with iron or zinc, and the portion of the aluminum - iron or less chromium. Spinel is formed in the contact-metasomatic rocks, skarns. Accumulating in the alluvial deposits, associated with magnetite, idocrase, pyroxene, garnet, chlorite.

The spinel is transparent. Color is various shades of red, pink, blue, oboe, green, yellow, brown, violet, orange, purple, purple, colorless, black, dark blue, dark brown, some difference have aleksandtrit effect or asterism of 4 or 6 the ray of the star. Spinel can have the following colors: galaxite dark red to black, black hercynite, picotit - dark green, dark brown, black, manganites green, gray-green, black.

There are the following kinds of spinel: noble - clear crystals; ordinary with a high content of iron, dark brown, black or dark green; black chrome, chrome portion of the aluminum is substituted; manganites - zinc spinel, where magnesium is substituted by iron and zinc.

Since ancient times, spinel different colors are used in jewelry.

Colorless spinel is used as an imitation diamond. It handles various types of cut, with effect asterism - in the form of cabochons.

Deposits: US, Sri Lanka, Italy, Thailand, France, Germany, Finland, India, Australia, Japan, Afghanistan, Burma, etc. The most famous deposits of red spinel - deposits of Mogok Valley in Myanmar, where the stone is mined there along with ruby as well as how to distinguish spinel and ruby eye impossible.

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