Plagioclase Feldspar
Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/12584677@N06">Leo-setä</a> (CC BY 2.0)
Mineral NamePlagioclase Feldspar
Chemical Formula(Na,Ca)(Al,Si)AlSi2O8
Mohs Hardness6
Crystal Systemtriclinic
Lustervitreous
Streak Colorwhite
Cleavageperfect in two directions (86° and 94°)
Fractureuneven
Specific Gravity2.68
Colorswhite, gray, bluish-white, greenish-white
Transparencytransparent
Type LocalityWorldwide (common rock-forming mineral)
Mineral GroupSilicates
Usesindustrial, construction, gemstone
Associated Mineralspyroxene, olivine, amphibole, quartz, magnetite
Raritycommon
Description
A microscopic view of elongated, lath-like crystals exhibiting various bright interference colors and polysynthetic twinning under polarized light, characteristic of plagioclase feldspar, set within a darker, finer-grained matrix.
Geological Context
Plagioclase feldspar is a primary rock-forming mineral, especially abundant in igneous rocks (mafic to felsic) such as basalt, gabbro, and granite, and also common in many metamorphic rocks and detrital sediments. The texture in the image suggests an igneous origin.
