Occurs as a rare secondary mineral in veinlets through metamorphosed manganese deposits )Sweden); in a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA).
IMA Status:
Valid Species (Pre-IMA) 1884
Locality:
In Sweden, from the Moss and Brattfors mines, Nordmark, and at Langban, Varmland. From Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA. Link to MinDat.org Location Data.
Name Origin:
From the Greek, to change, a reference to the strong pleochroism.
Chemical Formula: 