An isomorphous mineral of spinel group. A wide range of colors and shade of gemstone. Red-orange is named as flame spinel, an iron-rich dark-green to black, which is known as green spinel, pleonaste or ceylonite, grass-green as chlorospinel (iron-rich), brownish-black as picotite. Galaxite is a black ferrous oxide rich spinel, blue zinc-rich as gahnospinel, Nin is local term for black spinel from Thailand. Some specimen with prefix or suffix are erroneously named as ruby or sapphire such as fine red as ruby spinel (in Roman times as ballas ruby), and balas spinel or spinel sapphire. Misnomered are orange-yellow as rubicelle, almandine spinel. Another stone frequently misnomered as spinel such as Arizona spinel or Kandy spinel, both of which are garnet. Star spinel with 4 and 6-rayed stars are extremely rare. Cut as faceted gems in the brilliant cut, step cut, emerald cut, or mixed cut. Famous spinel gems are: over 500 cts., a stone in National Jewel Treasury of Iran, Black Prince's Ruby estimated 170 cts.
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