Peristerite

Periterite is a type of feldspar that has iridescence (like labradorite) and adularescence (like moonstone). Peristerite is reported to be albite, the sodium-rich end member of the plagioclase group of feldspar, which includes labradorite (sodium an calcium mixxed). When I analyzed these samples with x-ray diffraction,they came back as andesine (about 25% calcium, 75% sodium). Andesine was released to the gemstone market as a red and green mineral from China, but these gem “andesine” were later found to be artificially colored and not truly andesine.

Peristerite is a pale gray-blue variety of the plagioclase feldspar group, and some of the samples have yellow in them as well. Other gem minerals in the feldspar group include sunstone, moonstone, labradorite, and amazonite.