biotite

American  

[bahy-uh-tahyt] / ˈbaɪ əˌtaɪt /

noun

1. a very common mineral of the mica group, occurring in black, dark-brown, or dark-green sheets and flakes: an important constituent of igneous and metamorphic rocks.

---

biotite British  

/ ˈbaɪəˌtaɪt, ˌbaɪəˈtɪtɪk /

noun

1. a black or dark green mineral of the mica group, found in igneous and metamorphic rocks. Composition: hydrous magnesium iron potassium aluminium silicate. Formula: K(Mg,Fe) 3 (Al,Fe)Si 3 O 10 (OH) 2 . Crystal structure: monoclinic

---

biotite Scientific  

/ bī′ə-tīt′ /

1. A dark-brown or dark-green to black mica. Biotite is monoclinic and is found in igneous, metamorphic, and sedimentary rocks. Chemical formula: K(Mg,Fe) ₃ (Al,Fe)Si ₃ O ₁₀ (OH) ₂ .

---

Other Word Forms

Derived Forms

• biotitic
  adjective

Etymology

Origin of biotite

1860–65; named after J. B. Biot (1774–1862), French mineralogist and mathematician; see -ite ¹

Example Sentences

Geochemical fingerprinting of the widespread Toba tephra using biotite compositions.

From Nature • Mar. 11, 2018

Two frequently found micas are dark-colored biotite, frequently found in granite, and light-colored muscovite, found in the metamorphic rock called schist.

From Textbooks • Jan. 1, 2017

Figure 5.10 A granitic rock containing biotite and amphibole which have been altered near to the rock’s surface to limonite, which is a mixture of iron oxide minerals.

From Textbooks • Jan. 1, 2015

Commonly even very felsic rocks will not have biotite or muscovite because they may not have enough aluminum or enough hydrogen to make the OH complexes that are necessary for mica minerals.

From Textbooks • Jan. 1, 2015

They are excessively variable in their mineralogical composition, and very often alternate in thin seams with biotite hornfels and indurated quartzites.

From Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 6 "Home, Daniel" to "Hortensius, Quintus" by Various