Topaz
Topaz is one of the most popular gemstones when it comes to jewellery making, due to its strength, durability, availability and abundance within the Earth. It is also formed in some of the world largest crystal structures. For instance, the transparent topaz which was found in Minas Gerais, Brazil, weighed an astounding 596 pounds (or 271 kilos).
The most treasured variety of this gemstone is the Imperial Topaz, which has a striking golden orange-yellow appearance. This stone can also form with orange-brown or orange-pink colours.
This variety of topaz has the most desirable hues, but is also the rarest amongst them all – meaning that this stone is sold at the highest value. In fact, it is so rare within the market that it is known as a collector’s gemstone item. A pair of imperial topaz earrings with ruby and diamond points sold at Christies auction in 2010 for a whopping $650,000.
Rutilated topaz is a variety of clear topaz which has long needle-like inclusions through its body, giving it a striking appearance. It gains its name from its strong resemblance to the rutilated quartz variety, however this gemstone doesn’t contain mineral rutile at all – its needle inclusions are formed by limonite.
Many other topaz varieties gain their name and appearance from irradiation and heat treatment. Blue topaz are incredibly common in the jewellery market due to their ease to create and their striking beauty. London blue topaz is the most expensive variety of these heat treated stones due to its ink-like interior.
Azotic topaz has been treated to create a metallic coat around its body, so when moved in the sunlight it appears to have a rainbow sheen to its exterior.
Citrine
The citrine is a variety of quartz which occurs in a pale yellow to brownish orange colour. It used to be incredibly rare in the market and often confused with topaz – however, its attractive colour, durability, and ability to be created by heat treatment now makes it just as popular as the topaz. It is incredibly affordable and one of the most popular yellow gemstones available in the trade.
Natural citrine is incredibly hard to come by due to its rarity in the Earth, but it is easily distinguishable from its heat-treated counterparts. Lemon quartz, a light to dark yellow variety, is a natural-formed citrine with a true yellow colour.
Heat-created citrines always have an orange/brown/reddish tint to its body, whereas natural citrines do not – such as lemon quartz. This stone has recently experienced a popularity increase in the market and sells for a pretty penny.
Different shades of heat treated citrines have different names. Those which have a highly desirable deep-red orange colour are named Fire Citrine, and those which are vibrant orange are named Palmeria citrine. Maderia citrines are the most sought after however, ranging from golden orange to reddish-brown.
Ametrine is a beautiful mixture of citrine and amethyst, creating swirling colours of purple and yellow-orange. The colour zones are often sharply divided, displaying a gorgeous checkboard pattern or clear divide between the two quartz types.
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Written by Victoria Fletcher