pyrolusite

[pahy-ruh-loo-sahyt, pahy-rol-yuh-sahyt]
noun
a common mineral, manganese dioxide, MnO 2 , the principal ore of manganese, used in various manufactures, as a decolorizer of brown or green tints in glass, and as a depolarizer in dry-cell batteries.

Origin:
1820–30; pyro- + Greek loûs(is) washing + -ite1

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World English Dictionary
pyrolusite (ˌpaɪrəʊˈluːsaɪt)
 
n
a blackish fibrous or soft powdery mineral consisting of manganese dioxide in tetragonal crystalline form. It occurs in association with other manganese ores and is an important source of manganese. Formula: MnO2
 
[C19: from pyro- + Greek lousis a washing +-ite1, from its use in purifying glass]

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pyrolusite

common manganese mineral, manganese dioxide (MnO2), that constitutes an important ore. Always formed under highly oxidizing conditions, it forms light-gray to black, metallic, moderately heavy coatings, crusts, or fibres that are alteration products of other manganese ores (e.g., rhodochrosite); bog, lake, or shallow marine products; or deposits left by circulating waters. It is mined in Germany, Brazil, India, the United States, Cuba, Morocco, Ghana, and South Africa. Pyrolusite is used in the manufacture of steel and manganese bronze; in dry cells; and as a decolorizing agent in glass. For detailed physical properties, see oxide mineral (table)

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The deposit was composed mostly of pyrolusite and upgraded seaports and power stations.
Pyrolusite is abundant in cracks and pods along outcrops of deposits that consist principally of psilomelane in depth.
There is thus no scheelite recovery process or pyrolusite concentration technique per se.
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