Orientite

orientite

tangeite

pyrolusite

macfallite

Images

Formula: Ca8Mn3+10(SiO4)3(Si3O10)3(OH)10.4H2O
Sorosilicate (Si2O7 groups), manganese-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 3.05 to 3.33 measured, 3.48 calculated
Hardness: 4½ to 5
Streak: Brown
Colour: Deep red to brown, maroon
Solubility: Soluble in hot hydrochloric acid; insoluble in nitric acid
Common impurities: Al,Fe,V,Cu,Mg,K,H2O,S
Environments:

Sedimentary environments
Basaltic cavities

Orientite is of low temperature origin and forms in low alumina conditions, occurring with jasper, psilomelane, manganite and baryte (Dana).

Localities

At the type locality, the Firmeza District, Santiago de Cuba Province, Cuba, orientite occurs in manganese ore bodies in trachyte-like rocks and andesite tuff, agglomerates and limestone, associated with todorokite, manganite, pyrolusite neotocite, ferruginous chalcedony, baryte, low quartz, calcite, analcime, stilbite, chabazite and laumontite (HOM).
Orientite from the Firmeza District - Image

At the Manganese Mine, Copper Harbor, Grant Township, Keweenaw County, Michigan, USA, orientite is associated with manganite, braunite, macfallite and pyrolusite all replacing calcite in fissures and lenses in basalt (Dana, HOM, R&M 89.6.508).
Orientite from Keweenaw County - Image

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