Topaz with Mica, from Erongo, Namibia (REF:TPEN2)

Topaz is an aluminium silicate fluoride hydroxide crystal, 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 colours for Topaz include gold, blue, pink, brown, orange, colourless and a few other rarer shades such as pale green and red.

Colourless Topaz is sometimes irradiated artificially to create various shades of blue.

Topaz crystals of up to 220 pounds have been found, and Topaz gems weighing thousands of carats are in the Smithsonian Institution’s collection.

The Mica group of sheet silicate minerals includes several closely related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms.

The word mica is derived from the Latin word mica, meaning a crumb, and probably influenced by micare, to glitter.