biotite, also called black mica, a silicate mineral in the common mica group. It is abundant in metamorphic rocks (both regional and contact), in pegmatites, and also in granites and other intrusive igneous rocks. For chemical formula and detailed physical properties, see mica (table).

What are the characteristics of biotite?

Properties. Like other mica minerals, biotite has a highly perfect basal cleavage, and consists of flexible sheets, or lamellae, which easily flake off. It has a monoclinic crystal system, with tabular to prismatic crystals with an obvious pinacoid termination.

What is biotite used for in everyday life?

Biotite is used to determine the age of rock through the process of argon-argon dating or potassium-argon dating. Biotite can be used to determine the minimum age of rock and profile its temperature history. Sheet mica is important in the electronics industry as an electrical and thermal insulator.

Where is biotite found in the world?

Location: Biotite is found in many rocks around the world. Noteable deposits are found in Evje, Norway; Bessnes, France; Uluguru mountains in Tanzania; Ontario, Canada; and Laacher See, Germany.

Is biotite a clay mineral?

Biotite is a very common and widespread mineral group. The minerals of the group occur often in metamorphic and igneous rocks. It is much less common in sediments and sedimentary rocks because it yields to clay minerals in the weathering environment. Biotite is one of the two most common members of the mica group.

What is a biotite schist?

For example, a quartz-feldspar-biotite schist is a schist of uncertain protolith that contains biotite mica, feldspar, and quartz in order of apparent decreasing abundance. Lineated schist has a strong linear fabric in a rock which otherwise has well-developed schistosity.

What is biotite Colour?

Color – generally pleochroic, typically in shades of brown, but also can be yellow, green or red. Common biotite is one of the most strongly colored minerals seen in thin section. For biotite with low Fe-content (phlogopite), coloration is more subtle (clear, light browns and tans).

What is the crystal system of biotite?

Biotite–K(Mg,Fe)3AlSi3O10(OH)2–is a dark, iron-rich mica that has a monoclinic crystal system. The octahedral layer is entirely occupied by Mg2+ and Fe2+ and the mineral is therefore trioctahedral, since all octahedra are occupied.

How is feldspar used?

Feldspars play an important role as fluxing agents in ceramics and glass applications, and also are used as functional fillers in the paint, plastic, rubber and adhesive industries.

Can biotite scratch glass?

Since glass is generally harder than biotite, biotite does not scratch glass.

Why is biotite called Black mica?

This mineral is sometimes called “iron mica” because it is more iron-rich than phlogopite. It may also be called “black mica,” to distinguish it from “white mica” (muscovite)—both are formed in some rocks, sometimes side-by-side. Like other mica minerals, biotite has a highly perfect basal cleavage.

Where in the US can biotite be found?

Biotite occurs in the lava of Mount Vesuvius, at Monzoni, and many other European locations. In the United States, it is found in the pegmatites of New England, Virginia and North Carolina, as well as in the granite of Pikes Peak, Colorado. Biotite was named in honor of the French physicist Jean Baptiste Biot.

How is biotite created?

Biotite is a rock-forming 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.

Where can biotite granite be found?

This rock comes from Ballachulish, Scotland in the UK and is an excellent rock for educational use to describe the variations of granite which can be found.

What type of rock is biotite gneiss?

This rock is mostly composed of creamy-white feldspar and quartz, together with dark minerals, of which the most abundant is the dark mica biotite. The dark minerals are arranged in a streaky banding, giving the rock a gneissic texture.

What type of rock is basalt?

Basalt. Basalt is a hard, black volcanic rock. Basalt is the most common rock type in the Earth’s crust. Depending on how it is erupted, basalt can be hard and massive (Figure 1) or crumbly and full of bubbles (Figure 2).