Sections
Thumbnails

Biotite group crystals - click for larger pic
Biotite group crystals
Photo by Violet Anderson
© Royal Ontario Museum

Biotite group crystals - click for larger pic
Biotite group crystal
Photo by Doug Merson
© Doug Merson

Biotite group crystals - click for larger pic
Biotite group crystals
T. Kennedy photo
© T. Kennedy

Search this site

Powered by FreeFind



Biotite
K(Fe2+,Mg)3(AlSi3O10)(OH,F)2

     Biotite, one of the several members of the mica group found at MSH is fairly abundant in many environments and as a rock-forming mineral. It is difficult to distinguish from annite.

PHYSICAL CHARACTERISTICS:

Color is usually dark red brown to black.
Luster is vitreous to submetallic.
Diaphaneity is transparent to opaque.
Crystal System is monoclinic; C2/m.
Crystal Habits include short to long pseudohexagonal prisms
   to several centimeters across.
Cleavage {001} is perfect.
Fracture is not apparent due to cleavage.
Hardness is 2.5 - 3.
Specific Gravity is approximately 2.8 g/cm3.
Streak is white.
Associated Minerals include aegirine, analcime, gmelinite,
   gonnardite, microcline, monteregianite, natrolite and zircon.
Distinguishing Features: Crystal habit.
Origin: Named in 1847 after Jean Baptiste Biot (1774-1862),
   French physicist and chemist who first called attention to the
   optical difference in micas.

CLASSIFICATION:

Dana System
# 71.2.2b.2

Strunz Classification
# VIII/H.11-40

REFERENCES:
MinRec 21:299 (1990), Dana 8:1458-1460 (1997)

DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:

MSH
¤¤¤

PE
¤¤

AP
¤¤

MX
¤¤

SS
¤¤

MC
¤¤

HF
--

BR
¤¤

SX
--

FR
¤¤

Legend