The iron-rich annite-siderophyllite endmember of the Biotite mica series, typically dark green to black. It's a grounding stone aiding in clear perception and organized thought.
Dark Green, Brownish-Green, Black, forms platy sheets
Siderophyllite is classified as a silicate mineral mineral which typically crystallizes in the monoclinic system. Its chemical formula is KFe2+2Al(Al2Si2)O10(F,OH)2. Common crystal habits include micaceous foliated; pseudohexagonal crystals.