Chemical Composition Of Biotite

201921mineral name biotite chemical composition kmg,fe 2 3al,fe 3si 3 o 10 oh,f 2olor biotite is most commonly dark black, but it can also be dark brown and even dark green 5treak finding the streak of biotite can be quite difficult due to the weakness of the mineralhen testing the streak, it is common for it to flake off and appear to produce a brown streak however, this.