Moonstone
Image: Darla Sondrol (CC0)
Mineral NameMoonstone
Chemical FormulaNa(90-70%)Ca(10-30%)(Al,Si)AlSi2O8
Mohs Hardness6.5
Crystal Systemtriclinic
Lustervitreous
Streak Colorwhite
CleavagePerfect in two directions, nearly at 90 degrees ({001} perfect, {010} good)
Fractureuneven
Specific Gravity2.64
Colorswhite, gray, blue, peach, pink
Transparencytranslucent
Type LocalityNorway
Mineral GroupSilicates
Usesjewelry, collector
Rarityuncommon
Description
A translucent, whitish-gray mineral specimen, likely exhibiting a soft, shimmering adularescence characteristic of moonstone.
Geological Context
Moonstone, a variety of feldspar (often orthoclase or oligoclase), forms in igneous rocks such as pegmatites and granites, and occasionally in metamorphic rocks.
