Tancoite
Tancoite is an IMA-recognized mineral species in the phosphate class, with the chemical formula LiNa₂Al(PO₄)(PO₃OH)(OH).
It crystallizes in the orthorhombic crystal system (space group Pbcb).
Key properties: Mohs hardness 4–4.5; specific gravity 2.752; White streak; Vitreous luster; optically biaxial.
IMA symbol Tco, IMA status: approved, named in 1979.
Found in cavities in dump material from a complex granite pegmatite.
It is found associated with Lithiophosphate, apatite, spodumene, cookeite, barite, calcite, quartz.
The name refers to the Tanco mine, Canada, its original locality.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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