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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
chalcedony variety jasper,
psilomelane,
manganite and baryte
(Dana).
At Lake Manganese, 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).
At the type locality in what was Oriente 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).
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