Biotite

K(Mg,Fe)3(AlSi3O10)(OH)2

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Biotite is a common phyllosilicate mineral found in igneous and metamorphic rocks. It is distinguished from muscovite by its darker color due to iron and magnesium content. Biotite is an important indicator of metamorphic grade.

Crystal System Monoclinic
Mineral Class 09 Silicates
Mohs Hardness 2.5-3.0
Specific Gravity 2.70-3.40
Color Black, dark brown, dark green
Luster Vitreous
Streak White to gray
Cleavage Perfect basal {001}
Fracture Uneven
Transparency Translucent
Crystal Habit Tabular, pseudo-hexagonal

Mohs Hardness

Mohs Hardness: 2.5 – 3.0
1 Soft10 Hard

Crystal System

Monoclinic

Frequently Asked Questions

What is the hardness of Biotite?
Biotite has a Mohs hardness of 2.5-3.0.
What crystal system does Biotite belong to?
Biotite crystallizes in the Monoclinic crystal system.
What color is Biotite?
Biotite is typically Black, dark brown, dark green.
What type of luster does Biotite have?
Biotite exhibits a Vitreous luster.
What is the chemical formula of Biotite?
The chemical formula of Biotite is K(Mg,Fe)3(AlSi3O10)(OH)2.