Topaz

Characteristics

• Habit - prismatic
• Form - orthorhombic
• Hardness - 8 (hard)
• Cleavage - perfect
• Fracture - subconchoidal to uneven
• Streak - colourless
• Lustre - vitreous
• Colour - orange-brown, apricot, pink, blue

Introduction

Can fade if left in sun for too long, avoid rough handling as perfect clevage (can be seen in the larger crystals).

Characteristic lozenge-shaped cross sections and striations parallel to the length; occurs in granites, rhyolites, pegmatite dykes and hydrothermal veins.

Brilliant cut, colourless topaz can be mistaken for diamonds as have high refractive index; world's largest faceted topaz weights over 36,000 cts.

Lore: if kept in the home it would radiate good health for inhabitants; Nov birthstone; name thought to come from Sanskrit tapaz for 'fire';

Sources: Early discoveries from Russia and Brazil were called 'Imperial Topaz', were sherry-brown colour and could be heated to a bright pink. Today most are from Brazil. Most common on the market are blue stones produced by irradiation and colourless, which have been coated to produce coloured or iridescent stones; Ouro Preto region of Brazil supplies most of the world's yellow, orange and pink topaz for over 300 years; new discoveries in Pakistan.

Sherry topaz: (V&A) bodice ornament composed of bow and flowers. Two large golden-yellow topaz called 'sherry topaz'. Colourless stones in the arrangement are a mix of topaz (slight pink tinge) and rock crystal. Massive export from Port. Brazil in 18th century and is possible the ornament was made in Portugal. Propbably survives because of the cheap colourless stones - if diamonds would have been broken up.