Orientite Locality: Manganese Mine, Copper Harbor, Keweenaw County, Michigan, USA Original description: Collected 2011 by D. Maietta. Field of view is 0.68mm Lens: Nikon M Plan 20 F-stop: N/A Mounting: Normal, extension = 210 mm FOV: 0.68 mm Lighting: Dual fiber partially diffused Processing: CombineZP do-stack — Photo: David M. Maietta · CC BY 3.0
Orientite
Orientite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₈Mn³⁺₁₀(SiO₄)₃(Si₃O₁₀)₃(OH)₁₀·4H₂O.
It crystallizes in the orthorhombic crystal system (space group P2mm).
Key properties: Mohs hardness 4.5–5; specific gravity 3.05–3.33; Brown streak; Resinous, semimetallic; pitchy to dull when included luster; optically biaxial.
IMA symbol Orn, grandfathered status — known before the IMA’s founding, named in 1921.
Found in manganese orebodies in latite and andesite tuffs, agglomerates, and limestones (Oriente Province, Cuba); replacing calcite in fissures and lenses in basalt (Manganese Lake, Michigan, USA).
It is found associated with Todorokite, manganite, pyrolusite, neotocite, barite, quartz, calcite (Oriente Province, Cuba); braunite, manganite, calcite (Manganese Lake, Michigan, USA).
The name refers to the occurrence in Oriente Province, Cuba.