Definition of "pleonaste" []

• A black variety of spinel. (noun)

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• "It is simply titaniferous iron, iserine, pleonaste, ilmenite [Footnote: Or peroxide of iron, with 8 to 23 per cent, of blue oxide of titanium.] and degraded itabirite, the iron and quartz formation so called in the Brazil; and it is the same mineral which"