Pinakiolite Locality: Långban , Filipstad , Värmland , Sweden ( Locality at mindat.org ) Size: 6.7 x 5.4 x 3.4 cm. Pinakiolite is a very rare magnesium, manganese borate, unique in the world to the Langban deposit in Sweden. This is a fine, very rich specimen of large, lustrous, deep reddish-black laths to 1.2 cm concentrated in parallel-growth on the front of the specimen. Pinakiolite grains are richly peppered on both the front and back of the piece. Ex. Mullane Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Pinakiolite
Pinakiolite is an IMA-recognized mineral species in the borate class, with the chemical formula (Mg,Mn)₂(Mn³⁺,Sb⁵⁺)O₂(BO₃).
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 6; specific gravity 3.88; Brownish gray streak; Metallic, brilliant on {010}, to pearly luster; optically biaxial.
IMA symbol Pki, grandfathered status — known before the IMA’s founding, named in 1890.
A rare mineral found in banded granular dolomite in a metamorphosed Fe–Mn orebody.
It is found associated with Hausmannite, tephroite, berzeliite, manganophyllite, dolomite, calcite.
Its name comes from the Greek for a small tablet, in allusion to the thin tabular habit.