Cordierite
Image: <a href="//commons.wikimedia.org/wiki/User:Strekeisen" title="User:Strekeisen">Strekeisen</a> (CC BY-SA 4.0)
Mineral NameCordierite
Chemical Formula(Mg,Fe)2Al4Si5O18
Mohs Hardness7
Crystal Systemorthorhombic
Lustervitreous
Streak Colorwhite
Cleavageindistinct to poor on {010}
Fractureconchoidal to uneven
Specific Gravity2.65
Colorsblue, violet, yellowish, gray, brown, colorless
Transparencytransparent to translucent
Type LocalityNot specified
Mineral GroupSilicates
Usesgemstone, ceramic applications, scientific interest
Associated Mineralsquartz, feldspar, biotite, muscovite, garnet, sillimanite
Rarityuncommon
Description
This microscopic image, taken under crossed nicols with a compensator, reveals an altered cordierite crystal within a granite, displaying vivid interference colors of blue, purple, red, and yellow, with intricate textures indicative of alteration.
Geological Context
Cordierite typically forms in high-grade metamorphic rocks and some igneous rocks, such as granites that have assimilated aluminous material. Its presence indicates specific pressure-temperature conditions, and alteration suggests subsequent retrograde metamorphism or hydrothermal activity.
