Archive for the Amorphous Category

Opal

Refractive Index : 1.450 (+0.020 – 0.080)

Optical Characteristic : SR, ADR

Specific Gravity : 2.15 (+0.08 – 0.90)

Formula : SiO2.n(H2O) (water content usually 3 to 10%, but can be as high as 20%)

Crystal System : Non-crystalline

Variety/Species : white opal – translucent to semitranslucent with play-of-color against a white bodycolorBlack opal – translucent to opaque with play-of-color [...]