Tinzenite , Calcite Locality: Wessels Mine (Wessel's Mine), Hotazel, Kalahari manganese fields, Northern Cape Province , South Africa ( Locality at mindat.org ) Size: 4.5 x 3.5 x 3 cm. Charlie says this is by 2 orders of magnitude the best of species, and I believe him. Even more surprising is the locality, as I’d never heard of tinzenite from South Africa before. These crystals have the color of the best serandite and lustre like glass. They reach 1.5 cm in size. Overall, it’s an extraordinarily beautiful specimen that is also of mineralogical significance. Ex. Charlie Key. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Tinzenite
The manganese member of the axinite group — yellow-brown to violet bladed crystals.
Intro adapted from Wikipedia (CC BY-SA).
Tinzenite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂Mn²⁺₄Al₄[B₂Si₈O₃₀](OH)₂.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Axinite structural group.
Key properties: Mohs hardness 6.5; specific gravity 3.35–3.43; [Vitreous.] luster; optically biaxial.
IMA symbol Tnz, IMA status: approved, named in 1968.
Found in metamorphosed manganese-bearing ophiolites (Liguria, Italy); in quartz veins in cherts of the greenschist facies (Akatore, New Zealand).
It is found associated with Braunite, quartz.
The name is derived from the locality near Tinzen, Switzerland.