Wannenköpfe Quarry, Ochtendung, Maifeld, Mayen-Koblenz, Rhineland-Palatinate, Germany

K(Fe^₂₊/Mg)₂(Al/Fe^₃₊/Mg)([Si/Al]Si₂O₁₀)(OH/F)₂

Crystal System: monoclinic
Colour: dark  red, brown or green- brown
Habitus: foliated (or micaceous or layered)
Hardness: 2.5-3
Fracture: irregular<
Cleavage: {001} perfect
Density: 2.78-3.3  g/cm³
Origin and geological occurrence: it belongs to the mica group. Formally "biotite" is not a mineral; the name has been retained for historical reasons to indicate intermediate members in the solid solution between phlogopite and annite.

www.mindat.org
Smorf link

Samples:

9E.8 Biotite Dark brown micaceous aggregates of “biotite” with quartz and feldspar. #phyllosilicates

9E.10 Biotite Blackish micaceous crystals with quartz and feldspar. #phyllosilicates

	9E.11 Biotite Brownish micaceous crystals with feldspar and quartz. #phyllosilicates
	9E.15 Biotite Aggregate of micaceous crystals. #phyllosilicates