- Color: blue, yellow, pink, red, brown, green, colorless
- Hardness: 8
- Refractive index: 1.60 - 1.64
- Density: 3.50 - 3.58
- Chemical composition: Al2[SiO4](F,OH)2
- Crystal structure: orthorhombic
- Origins: Brazil, Madagascar, Russia, USA, Mexico, Pakistan.
Most valued color for topazes is orangey pink (imperial topaz from Brazil). Heat treatment is usual for yellowish stones; color of light blue or colorless stones can be enforced by x-ray treatment and heating. Very big clean crystals are common. Prices subject to noticeable variation due to fashion trends on local markets.