Topaz is an aluminium silicate fluoride hydroxide crystal with a hardness of 8. Its crystal structure is orthorhombic, and it frequently forms prismatic crystals, often eight-sided with striations along the length. Many have diamond-shaped cross sections and pyramidal terminations. Topaz is found in Brazil, Sri Lanka, Russia, Burma, Australia, Japan, Madagascar, Mexico, Africa and the USA. Natural colors for Topaz include gold, blue, pink, brown, orange, colorless and a few other rarer shades such as pale green and red. Colorless Topaz is sometimes irradiated artificially to create various shades of blue.