Topaz makes an ideal gem. A good hardness and desirable colors, combined with a relative abundance and availability makes it one the most popular gemstones. The most valuable colors of Topaz are the golden orange-yellow type, called Imperial Topaz, and the dark pinkish-red and orange-red colors. Value increases with a deepness of color in orange and reddish hues. The most commonly used colors of Topaz in jewelry are the blue types. It was not until this past century that blue Topaz became widespread on the gem market, since virtually all blue gem Topaz is irradiated and heat treated.<br /><br />Topaz obtains much of its popularity from its beautiful colors and its status as a birthstone. Natural topaz colors include rare and valuable yellow, orange, pink, red, purple, and blue. The most affordable and frequently purchased is blue topaz that has received its color from treatment.<br /><br />In 1812, Friedrich Mohs developed a set of 10 standard minerals that could be used to assign a relative hardness to minerals and other materials. Today, over 200 years later, his hardness scale is used by students and geologists throughout the world to identify mineral specimens.<br /><br />Topaz can be found in Brazil, Russia, Pakistan, Mexico, the USA, Madagascar and Sri Lanka. In the 19th century, the main source for pink topaz was in the Ural Mountains in Russia. The imperial family, including the tsars, reserved exclusive rights to own and wear the colour, thus imparting the name 'Imperial topaz'. It is less common than other naturally occurring colours of topaz and is thought to resemble the colours of the setting sun.<br /><br />Topaz is a relatively hard material, with a level of 8 on the Mohs scale of hardness. While it can take a high polish and show a bright vitreous lustre, its perfect and easy cleavage lets it down. Cleavage is a directional breakage that occurs along a crystal plane in only crystalline materials. <br /><br />It should be noted that almost all pink topaz on the market today is mined in Brazil and heat-treated to bring out the pink colour. Natural blue topaz is typically pale, and stronger colours like 'London blue' or 'Swiss blue' are achieved by irradiating and heating a colourless topaz to promote and stabilize the blue colour.<br /><br />One colour that was not created by nature is known as 'mystic' topaz. It is a colourless topaz that has been coated with a thin metallic layer to produce extreme iridescence.