is a hydrous aluminium silicate of iron and magnesium with formula (Mg, Fe, Al)6(Si, Al)4Oi4(OH)8 and hardness of 3.
Is a member of the chlorite group and is not very common mineral.I am the first who decided to facet this material. The color is black , opaque and fair luster.
It comes from Keweenaw Co. Michigan.
A study performed by Henrich-Robinson ( The Mineralogy of Michigan 2004) describe the chlorite in this area as chamosite forming a solid solution series with clinochlore and the dark green to black chlorite has been proved to be chamosite.
Size: 9x9x5.5 mm.