Gems that form in the corundum with a titanium impurity are generally colorless. These gems are called white sapphires and can be quite beautiful. Corundum that forms with a chromium impurity is generally red in color and if it's gem quality, rubies can be made. If iron and titanium are both present, the gems that can be cut from it are blue. Colors such as yellow and purple may also be present depending on how the crystals form.
Corundum is the crystalline form of aluminium oxide. This mineral develops in mica schist and some metamorphic marble. Currently it is mined in Russia, Zimbabwe, Sri Lanka, India and Madagascar. It is also found in some places in the U. S. Corundum is a 9 on the Mohs scale making it almost as hard as diamond.
The hardness of the these gems makes them a better choice for jewelery than zircon which is considerably softer. Though it doesn't sparkle as much. Diamonds are in more demand and hence more expensive, colorless corundum is actually much more rare.
Since the ancient Roman Empire, gems have been heat treated to either deepen the color or make pale colored gems colorless. Colorless corundum gems may then be sold as white sapphires. Heat treated gems have a reduced value because the color may fade over time.
Corundum has more mundane value as well. Because of its hardness, it is popular as an abrasive. Though it need not be mined. For at least 150 years we have known how to grow corundum, and even gem quality corundum in a lab. Crystals of a much larger size can be grown with controlled conditions. These gems have fewer imperfections and can be distinguished from natural crystals by a trained jeweler, though they are chemically identical to those made by nature.
In short, these gems are a rare and beautiful gem. Because of the demand for diamonds, they are a more affordable alternative when a clear gem is needed. And because they are harder than zircon, they will be more durable in a given setting.
Corundum is the crystalline form of aluminium oxide. This mineral develops in mica schist and some metamorphic marble. Currently it is mined in Russia, Zimbabwe, Sri Lanka, India and Madagascar. It is also found in some places in the U. S. Corundum is a 9 on the Mohs scale making it almost as hard as diamond.
The hardness of the these gems makes them a better choice for jewelery than zircon which is considerably softer. Though it doesn't sparkle as much. Diamonds are in more demand and hence more expensive, colorless corundum is actually much more rare.
Since the ancient Roman Empire, gems have been heat treated to either deepen the color or make pale colored gems colorless. Colorless corundum gems may then be sold as white sapphires. Heat treated gems have a reduced value because the color may fade over time.
Corundum has more mundane value as well. Because of its hardness, it is popular as an abrasive. Though it need not be mined. For at least 150 years we have known how to grow corundum, and even gem quality corundum in a lab. Crystals of a much larger size can be grown with controlled conditions. These gems have fewer imperfections and can be distinguished from natural crystals by a trained jeweler, though they are chemically identical to those made by nature.
In short, these gems are a rare and beautiful gem. Because of the demand for diamonds, they are a more affordable alternative when a clear gem is needed. And because they are harder than zircon, they will be more durable in a given setting.
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