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Encyclopedia Britannica - Main :: PRE-PYR |
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PSILOMELANE , a mineral
manganese oxide
manganese manganate, but of doubtful composition. The amount of manganese present corresponds to 7o-8o% of manganous oxide
mineral
appearance , being from the Greek >GtXbs (naked, smooth) and fXas (black); a Latinized form is calvonigrite, and a German name with the same meaning is Schwarzer Glaskopf. Psilomelane is readily distinguished from other hydrous manganese oxides (manganite and wad) by its greater hardness (H. = 5 2) ; the sp. gr. varies from 3.7 to 4.7. The streak is brownish-black and the fracture smooth. Owing to its amorphous nature, the mineral often contains admixed impurities, such as iron hydrates. It is soluble in hydrochloric acid with evolution
iron mine at Lostwithiel in Cornwall
mined
Vermont
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