Mohs scale hardness: 7.5
Zircon is a zirconium silicate, often with some hafnium and occasionaly with some thorium, uranium and yttrium. Its structure can contain up to 20% of hafnon; if it exceeds that, then it is scientifically a different mineral, Hafnon. The zircon is a fiery gem that can be colorless, yellow, cognac brown, red, green or blue. The name is believed to have originated with the Persian word zargoon, which means “gold colored”.
Zircon Crystal Structure
Traces of radioactive elements are often contained in the zircon’s structure which causes it to be metamict. This cyrtolite (unstable form of zircon), is characterized by rounded and almost domal crystals which normally are pitchy or dull in luster. These metamict zircon crystals become stable when heated and revert to their normal structure of crystal. This also changes the transparency and color of the stone. In order to enhance the color and transparency, Zircon that is not radioactive can even be heated.
Zircon has two varieties, one is called Low Zircon and the other High Zircon. These two types of zircon vary only in their properties and gemologists use this nomenclature to differentiate between those two. Radioactive Zircon that has undergone the process of metamiction is occasionally called "Low Zircon", and stable Zircon with intact crystal lattice "High Zircon". Zircon crystal is one of the heaviest gemstones, it means that when compared to other gemstones of the same weight, zircon gem will look smaller in physical size.
Colors of Zircon
Natural zircon crystal originally comes in earthy brown, bright red, strong green and yellow. Treated or heated zircons can come in variety of colors from yellow, bright red, red, blue, purple, colorless white etc. The black color to dark brown observed in most Zircon crystals is due to the impurities of iron oxide. The green coloring in rounded pebbles usually indicates the Zircon as radioactive Cyrtolite variety. Zircon of good fine quality are always transparent. Any inclusions or visible flaws in the gemstone will diminish its value substantially. Zircon stone normally will keep changing its color when being heated.
Clarity and color are the most important considerations in evaluating Zircon gem. Deep red is the most beautiful, prized and rare color, next is pure, intense blue, sky blue, colorless, orange, brown and yellow are less valued. Pale blue zircons are sometimes called starlites and the reddish-brown ones are known as hyacinths.
Diamond Substitute & Simulants of Zircon
The colorless variety of zircon has a brilliant sparkle and makes a convincing diamond substitude. The high refractive index and dispersion of zircon cause it to approach diamond in fire and brilliancy. However, faceted zircons were sold as diamonds in the 14th century A.D. Gems like tourmaline, synthetic Spinel, sphene, garnet, diamond and quartz are some of the gemstones which resemble zircon. Colorless zircon are sometimes mistakenly called Matura diamonds, after a place in Sri Lanka where they are mined.
Today however zircons are commonly confused with cubic zirconia—the man-made diamond substitude, causing their popularity to wane. Zircon and cubic zirconia are totally separate materials and those two have no connection with each other. Colorless Zircon may be used as a Diamond fake, but it is still quite valuable in its own right, as oposed to the cheap, synthetic Cubic Zirconia.
Treatments and Uses
Natural untreated zircon crystals are today very rare, most of the zircons available in the market are heat-treated and the color of these heat-treated gems may change over time. Zircon can suffer from abrasion and the facets can be easily chipped with a slight knock, therefore the gems are often wrapped by gem dealers in individual pieces of paper so that the stones do not knock against each other.
Zircons are primarily found in sedimentary rocks, igneous rocks and metamorphic rocks. The least abundant type of zircon is the large zircon crystals. Zircon is one mineral that is found worldwide and is a very common accessory. Being the most important ore of zirconium, zircon is also the most important ore of the element hafnium, which is present oftenly in considerable quantities in zircon. In certain localities, Zircon is an ore of the radioactive element thorium also.
In ancient times zircon was believed to have curative powers and other mystic qualities. Zircons reached their peak in popularity during Victorian times when they were used extensively in brooches, pendants and pins. They are most appreciated by gem collectors who savor the variety of colors and brilliance of this lovely, natural stone. Zircon is also regarded as birthstone for December.
It is believed zircons have special properties:
- Used to fight evil and avoid jealousy and enviness.
- To protect people from insomnia and help to calm people down.
- Brings happiness and self-satisfaction.
Asian origins: Cambodia, Vietnam, Thailand, Sri Lanka and Myanmar.
Astrologically, zircon is associated with the zodiac sign of Sagittarius.
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