Listing description
Biotite is a name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks. These include: annite, phlogopite, siderophyllite, fluorophlogopite, fluorannite, eastonite and many others. These micas vary in chemical composition but are all sheet silicate minerals with very similar physical properties.
Detailed description
A generalized chemical composition for the biotite group is:
K(Mg,Fe)2-3Al1-2Si2-3O10(OH,F)2
The name "biotite" is used in the field and in entry-level geology courses because these minerals generally can not be distinguished without optical, chemical or x-ray analysis.
Biotite is a primary mineral found in a wide range of crystalline igneous rocks such as granite, diorite, gabbro, peridotite and pegmatite. It also forms under metamorphic conditions when argillaceous rocks are exposed to heat and pressure to form schist and gneiss. Although biotite is not very resistant to weathering and transforms into clay minerals, it is sometimes found in sediments and sandstones.
Properties of Biotite
Biotite is very easy to identify and with a little experience a person will be able to recognize it on sight. It is a black mica with perfect cleavage and a vitreous luster on the cleavage faces. When biotite is separated into thin sheets, the sheets are flexible but will break upon severe bending. When held up to the light the sheets are transparent to translucent with a brown, gray or greenish color. Experienced observers can sometimes recognize phlogopite by its brown color.
Physical
Properties of Biotite
|
|
|
Chemical Classification
|
dark mica
|
|
Color
|
black, dark green, dark brown
|
|
Streak
|
white to gray, flakes often produced
|
|
Luster
|
vitreous
|
|
Diaphaneity
|
thin sheets are transparent to translucent, books are opaque
|
|
Cleavage
|
basal, perfect
|
|
Mohs Hardness
|
2.5 to 3
|
|
Specific Gravity
|
2.7 to 3.4
|
|
Diagnostic Properties
|
dark color, perfect cleavage
|
|
Chemical Composition
|
K(Mg,Fe)2-3Al1-2Si2-3O10(OH,F)2
|
|
Crystal System
|
monoclinic
|
|
Uses
|
very little industrial use
|
Biotite Minerals
As noted above, biotite is a name used for a number of black mica minerals that have different chemical compositions but very similar physical properties. These minerals generally can not be distinguished from one another without laboratory analysis. A small list of the biotite minerals is given below with their chemical compositions.
|
Mineral
|
Chemical Composition
|
|
Annite
|
KFe3(AlSi3)O10(OH)2
|
|
Phlogopite
|
KMg3(AlSi3)O10(OH)2
|
|
Siderophyllite
|
KFe2Al(Al2Si2)O10(F,OH)2
|
|
Eastonite
|
KMg2Al(Al2Si3)O10(OH)2
|
|
Fluorannite
|
KFe3(AlSi3)O10F2
|
|
Fluorophlogopite
|
KMg3(AlSi3)O10F2
|
Uses of Biotite
Biotite has a small number of commercial uses. Ground mica is used as a filler and extender in paints, as an additive to drilling muds, as an inert filler and mold-release agent in rubber products, and as a non-stick surface coating on asphalt shingles and rolled roofing. It is also used in the potassium-argon and argon-argon methods of dating igneous rocks.
PRICE
$10/KG OR $4.54/IB
For more information:
mobile: +2348039721941
contact person: emeaba uche
e-mail: emeabau@yahoo.com
website: www.franchiseminerals.com
No comments:
Post a Comment