Sincosite , Minyulite Locality: Ross Hannibal Mine (North Star Mine; Hannibal Mine; and Mikado Mine), Lead District, Lawrence County, South Dakota , USA ( Locality at mindat.org ) A specimen with unusally deep green crystals, scattered about on matrix and with an associated spray of white, acicular minyulite. Exceptional quality and richness for this find (early 1990s by Tom Loomis), and such are scarce on the market today. 5.5 x 5 x 4 cm — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Sincosite
A green calcium vanadium phosphate discovered in 1922 at Sincos, Peru.
Intro adapted from Wikipedia (CC BY-SA).
Sincosite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca(VO)₂(PO₄)₂·4H₂O.
It crystallizes in the triclinic crystal system (space group P1). It is a member of the Sincosite structural group.
Key properties: Mohs hardness 1.5; specific gravity 2.84–2.98; Green streak; Vitreous, submetallic if partially dehydrated luster; optically uniaxial.
IMA symbol Scs, grandfathered status — known before the IMA’s founding, named in 1922.
Found in veinlets in black carbonaceous shale (Sincos, Peru).
It is found associated with Gypsum (Sincos, Peru); minyulite (Ross Hannibal mine, South Dakota, USA).
The name refers to its originally noted occurrence near Sincos, Peru.