Lesson plan
Ceylonite
Ceylonite (first cited 1793) and pleonaste (first cited 1801) or pleonast are dingy blue or grey-to-black varieties of spinel. Ceylonite, named for the island of Ceylon, is a ferroan spinel mineral with Mg:Fe from 3:1 and 1:1, and little or no ferric iron. Pleonaste is named from the Greek for 'abundant,' for its many crystal forms, and is distinguished chemically by low Mg:Fe ratios of approximately 1:3. It is sometimes used as a gemstone.
Article summary
Ceylonite (first cited 1793) and pleonaste (first cited 1801) or pleonast are dingy blue or grey-to-black varieties of spinel. Ceylonite, named for the island of Ceylon, is a ferroan spinel mineral with Mg:Fe from 3:1 and 1:1, and little or no ferric iron. Pleonaste is named from the Greek for 'abundant,' for its many crystal forms, and is distinguished chemically by low Mg:Fe ratios of approximately 1:3. It is sometimes used as a gemstone.
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Discussion questions
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