Biotite

 

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What is it and where is it formed?  Biotite is a mineral in the group called Mica.  It is usually found in igneous and metamorphic rock.  Biotite has radioactive elements in it that are used to figure out how old the mineral is.  It is sometimes found in chunks that are called books.  They look like squares with sheets as pages. 

How and where is it mined?  It is mined using quarrying and underground mining depending upon how far under the surface the mineral is.  It is found in Sudbury, Ontario, Sicily, and Russia.

What is it used for?  Biotite is mainly used for display in mineral collections.  One place we looked said it was a good heat insulator in industry but another source said that Biotite has no industrial uses. 

Biotite

Sheets of biotite are flexible.  They can be bent and go back to their original shape.
Mineral Characteristic What the
mineralogists say		 Kid's Guide:  What it REALLY means!
Chemical Symbol K2(Mg,Fe)3AlSi3O10(OH,O,F2)2 It has oxygen, silicon, magnesium, potassium, iron, aluminum, fluorine, and hydrogen in it.
Color Dark green, brown, or black These are the usual colors.  When it has a lot of iron in it, biotite is a darker color.
Streak White If you crushed this mineral, it would become white dust.
Transparency Transparent to translucent Depending on the piece, light will pass through it.  It is easier to understand that sometimes you can see through it clearly and other times it would be blurry.
Luster Glossy, vitreous, pearly If you shine a light on this mineral, it would look glossy or have a shine like pearls have.
Cleavage Perfect in one direction When it is broken, biotite perfectly splits into sheets or layers that can be split even more with a fingernail.
Fracture Uneven when seen It does not break into small pieces because it splits evenly into sheets first.
Magnetism None It will not attract, or be attracted to, a magnet.
Hardness 2.5 It is not very hard.  Sheets of biotite are flexible and can bend.
Specific gravity 3.0 Compared to an equal volume of water, this is slightly heavier.  If you held it in your hand, it would seem to be a little heavier than it looks like it would be compared to its size.
Crystal Shape Monoclinic

Links:

Citations:

“Biotite.”  21 Feb. 2006. <http://mineral.galleries.com/minerals/silicate/biotite/biotite.htm>.
 

Fuller, Sue.  Rocks & Minerals.  London: Dorling Kindersley, 1995.

 

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