ryakoniten.
Probably a misreading of rhyacolite n.
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the world > the earth > minerals > types of mineral > silicates > tectosilicate > [noun] > feldspar > orthoclase > varieties
adularia1789
ice-spar1816
necronite1819
murchisonite1827
rhyacolite1831
Amazon-stone1836
ryakonite1837
krablite1844
1837 J. D. Dana Syst. Mineral. 293 Feldspar. Spatum orthotomum... Ice spar. Ryakonite.
This entry has been updated (OED Third Edition, March 2011; most recently modified version published online March 2018).
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n.1837