ILVAITE
Ilvaite is a scarce calcium iron hydroxysilicate
mineral - CaFe+3(Fe+2)2O(Si2O7)(OH).
It has a black to very dark gray color, greenish-black to brownish-black
streak, striated elongate or platy crystals, and a hardness of 5.5 to 6.
It is principally found in some skarn deposits (it's a contact metamorphic
mineral).
Ilvaite
crystals (black) on quartz (greenish) from a skarn deposit in the Second
Sovietskiy Mine at Dalnegorsk, Maritime Province, eastern Russia.