Formula: Al2(SiO4)(F,OH)2

Colour: Colourless, white, pale blue, light green, yellow, yellowish brown, or red

Lustre: Vitreous

Hardness: 8

Specific Gravity: 3.4 – 3.6

Crystal System: Orthorhombic

Name: Named after Topasos Island in the Red Sea. In antique times, the name was probably used for the gemstone that is now known as Peridot.

Occurs in pegmatites and high-temperature quartz veins, also in cavities in granites and rhyolites.