Description
Mica or mica is the name for a large group of minerals. These minerals are phyllosilicates with the general formula (AB2-3X,Si)4O10(O,F,OH)2 where: A usually represents potassium, but can also be sodium, calcium, barium, or cesium. B can contain aluminum, lithium, iron, zinc, chromium, vanadium, titanium, manganese, and/or magnesium. X is usually aluminum, but can also be berillium, boron, and/or iron (3+). All micas crystallize in the monoclinic crystal system. However, many mica minerals appear to have six-sided crystal forms. In fact, these are not true hexagons, but pseudohexagons: they are only six-sided on the outside. Careful analysis (usually using X-ray diffraction) will always reveal the true, monoclinic identity of such crystals.
