rock crystal
Photo courtesy of Scott Papper, GIA GG, AJP, Global Gemology & Appraisals
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Variety: Rock Crystal
Species: Quartz Mohs Hardness: 7 out of 10 Color: Transparent and colorless with no phenomena RI: 1.544 to 1.553 (very constant) Birefringence: 0.009 SR/DR/AGG: DR Clarity Type: Type II Optic Character: Uniaxial positive. Might show a bull's eye or Airy's spiral optic figure and Brazil law twinning under crossed polarizing filters. Spectrum: Not diagnostic Fluorescence: Generally Inert SG: 2.66 (+0.03/-0.02) |