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A dark-brown or dark-green to black mica, K(Mg,Fe)3(Al,Fe)Si3O10(OH)2, found in igneous and metamorphic rocks.

[After Jean Baptiste Biot (1774-1862), French physicist.]

bi′o·tit′ic (-tĭt′ĭk) adj.
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Adj.1.biotitic - relating to or involving biotite
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References in periodicals archive ?
The Madrid Basin is bounded by three main mountain ranges: the Spanish Central System to the north (Somosierra mountains, composed of slates, phyllites and quartzites) and west (Guadarrama Sierra, mainly composed of granodiorites, biotitic granites, gneisses, pegmatites and schists), the Iberian Range to the east (mainly composed of limestones, dolostones, marls and arenites) and the igneous metamorphic series of the Toledo Mountains to the south (Aparicio-Yague and Garcia-Cacho, 1984; Calvo, 1989a; Villaseca et al.
72 is biotitic granodiorite from a large rock wall of a cirque of the Gharesa glacier (5 500 m, Fig.
hirsuta is not a cave in the true sense, but comprises an outcrop of granitic and biotitic feldsparic gneiss that split vertically, forming a narrow rock fissure that transects the outcrop from north to south and from top to bottom (Fig.
Sporadically, but especially in the eastern part of the lens and near the lower margin, dark brown biotitic mica is abundant.
All of the remaining samples were comprised of variations of the bulk host lithology of garnetiferrous, biotitic gneiss.