일반명 : 첨정석(스피넬) Spinel

원산지 : Luc Yen, Vietnam

무   게 : 88g(440ct)

크   기 : 45*37*33mm 

THE MINERAL SPINEL

·    Chemistry: MgAl2O4 , Magnesium Aluminum Oxide

·    Class: Oxides

·    Group: Spinel

·    Uses: as a gemstone and as a mineral specimen

·    The physical properties of spinel.

Spinel is a very attractive and historically important gemstone mineral. Its typical red color, although pinker, rivals the color of ruby. In fact, many rubies, of notable fame belonging to crown jewel collections, were found to actually be spinels. Perhaps the greatest mistake is the Black Prince's Ruby set in the British Imperial State Crown. Whether these mistakes were accidents or clever substitutions of precious rubies for the less valuable spinels by risk taking jewelers, history is unclear. The misidentification is meaningless in terms of the value of these gems for even spinel carries a considerable amount of worth and these stones are priceless based on their history, let alone their carat weight and pedigree.

PHYSICAL CHARACTERISTICS:

·  Color is red, green, blue, purple, brown, and black; but red is by far the more common color.

·  Luster is vitreous.

·  Transparency: Crystals are transparent to translucent and sometimes nearly opaque.

·  Crystal System: Isometric; 4/m bar 3 2/m

·  Crystal Habits include the typical octahedron, but can be found as dodecahedrons and combinations of other isometric forms. Also as rounded grains in alluvial placer deposits.

·  Cleavage: None

·  Fracture is conchoidal.

·  Hardness is 7.5-8.0

·  Specific Gravity is 3.6-4.0

·  Streak is white.

·  Other Characteristics: index of refraction is approximately 1.71 - 1.76 and rutile inclusions may produce six or four rayed stars or asterisms.

·  Associated Minerals include calcite, dolomite, corundum and garnets.

·  Notable Occurrences include Burma, Sri Lanka, Brazil and Afghanistan.

·  Best Field Indicators are twinned crystals if present, color, hardness, density and locality.