Biotite

biotite

What is biotite?

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 cannot be distinguished from one another without laboratory analysis.

Is biotite Black or white mica?

Black mica and white mica (muscovite) often occur together within a rock and may even be found side-by-side. Biotite isnt always black. It can be dark brown or brownish-green. Lighter colors also occur, including yellow and white. Like other types of mica, biotite is a dielectric insulator.

What is the difference between biotite and phlogopite?

Biotite, the more abundant of the two minerals, is the iron-rich end member of the series while phlogopite is the magnesium-rich end member. A common, widespread, rock-forming mineral, biotite is a significant mineral in granites, diorites, and igneous pegmatites.

Can biotite be uniaxial?

Pleochroic halos around radioactive minerals (zircon or allanite) are common. Some biotite may have a 2V of 0 o, is sensibly uniaxial. Twins with 001 composition planes are possible, but usually not observed Refractive indices increase with increasing iron content.

What is a biotite mineral?

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 cannot be distinguished from one another without laboratory analysis.

What is Biotite usually altered to?

Biotite is usually altered to clay minerals montmorillonite and vermiculite. Biotite and muscovite are the two most common mica minerals that often occur together in Al-rich igneous rock.

Is biotite the same as mica?

Although biotite is sometimes called black mica, it occurs in other colors, including brown, greenish-brown, yellow, and even white. Biotite occurs with other types of mica, even within a single rock. The primary use of biotite is to date the minimum age of rocks and geological features.

Is biotite a solid solution series?

2. It is primarily a solid-solution series between the iron - endmember annite, and the magnesium -endmember phlogopite; more aluminous end-members include siderophyllite and eastonite. Biotite was regarded as a mineral species by the International Mineralogical Association until 1998, when its status was changed to a mineral group.

What is the color of biotite in color?

Biotite and phlogopite are the darkest members of the mica mineral group. Typically brown to black in color, biotite occasionally occurs in a dark green variety. Phlogopite is lighter in color, typically being pale yellow to golden brown.

What is the composition of phlogopite?

Phlogopite Composition: A hydrous potassium magnesium aluminum silicate, KMg2Al2Si3Oio (OH)2. Usually contains about 3 percent of fluorine and some iron. Diagnostic Features: Characterized by its micaceous cleavage and yellowish brown color.

What is the difference between muscovite and biotite?

The key difference between muscovite and biotite is that muscovite contains mainly potassium and aluminium, while biotite mainly contains potassium and magnesium. Muscovite and biotite are phyllosilicate minerals.

What are the diagnostic features of phlogopite?

Diagnostic Features: Characterized by its micaceous cleavage and yellowish brown color. Distinguished from muscovite by its decomposition in sulfuric acid and from biotite by its lighter color. But it is impossible to draw a sharp distinction between biotite and phlogopite.

Postagens relacionadas: