Mica Group

Mica Group

Phlogopite

Hand Specimen identification: Phlogopite, an end member biotite, is identified by cleavage, color, and association. If not brown, it is indistinguishable from other biotites without additional analytical data. Chemical Composition : KMg3(AlSi 3O10)(OH)2 Hardness : 21/2 to 3 Specific Gravity2.8 Cleavage/Fracture : perfect basal (001)/elastic Luster/Transparency : pearly/transparent Color : …

Read More »

Biotite

Hand Specimen identification: Biotite is distinguished by its association, micaceous nature, and dark color. It may be confused with other micas, especially chlorite. Composition is variable and cannot be determined without detailed ana-lytical work. Chemical Composition : K(Mg,Fe)3(AlSi 3O10)(OH)2 Hardness : 21/2 to 3 Specific Gravity2.9 to 3.1 Cleavage/Fracture : …

Read More »

Margarite

Hand Specimen identification: Margarite is characterized by its micaceous nature, brittleness, and pearly luster. Association and brittle-ness usually distinguish it from other white micas. Chemical Composition : CaAl2(Al2Si 2O10)(OH)2 Hardness : 31 2 to 5 Specific Gravity3.1 Cleavage/Fracture : perfect basal (001)/uneven Luster/Transparency : vitreous/transparentto translucentvitreous/transparentto translucent Color : gray-yellow, …

Read More »

Lepidolite

Hand Specimen identification: Micaceous habit (see Figure 11), often a distinctive lilac-gray or rose color, and association usually serve to identify lepidolite. Chemical Composition : K(Li,Al) 2 – 3(AlSi 3O10)(OH)2 Hardness : 2.5 to 4 Specific Gravity2.9 Cleavage/Fracture : perfect basal {001}/uneven Luster/Transparency : pearly/translucent Color : perfect basal {001}/uneven …

Read More »

Muscovite

Hand Specimen identification: Micaceous character (Figure 10a) and silver color distinguish muscovite. It may be confused with other white micas, such as paragonite or margarite. Certain identification requires optical, X-ray, or chemical analysis. Chemical Composition : KAl2(AlSi 3O10)(OH)2 Hardness : 2 to 2 1 2 Specific Gravity2.8 Cleavage/Fracture : perfect …

Read More »