What makes rubies such a valuable gem?
Rubies have long been prized for their rich, red color. They've been worn by emperors and kings as well as the common man. In fact, according to the Gemological Institute of America, rubies gross the highest per-carat price of any other colored gemstone. This opulent gemstone can be found in the Ruby and Diamond Clusters earrings by the Brian Gavin team. However, you may not know too much about what makes the ruby such a valuable gem.
Rubies come from the corundum mineral, which is a form of aluminum oxide. On its own, corundum is transparent. The red color develops when small amounts of the aluminum atoms are replaced by chromium atoms. The color can range from orange-red to purple-red, with pure "Pigeon Blood" being the most popular hue.
Sapphires and rubies are virtually identical in every way but color. Ruby refers only to red gems, while sapphire includes all other colors. In fact, a ruby technically is a sapphire, but its prized color has always separated it from similar gems.
Corundum scores a nine on the Mohs hardness scale, which grades the strength of gem minerals. Diamonds are a 10. This is another reason ruby is so highly valued, along with the deep color and gorgeous shine.
Rubies can have fluorescent properties, which causes them to exhibit more brilliant shades of red when placed in sunlight. Fluorescent varieties are highly valued for this glowing property.
Where they form
Rubies are found in limited quantities. These gems have been known to be found in north-central Myanmar. The ruby occurs in bands of crystalline limestone, and is associated with granitic and gneissic rocks in this area of the world. The gem as also been found in gravel with sapphire in Thailand. The rubies found here often have a darker hue. Sri Lanka is another known site, though the color quality is usually not as high as those of the rubies found in Myanmar stones.
The four Cs
Diamond grading looks at the four Cs to assess value. The same goes for other gemstones. You already know the color properties of a ruby. Clarity is another important feature. Inclusions that affect the gem's transparency or brilliance decrease the value. Some inclusions - such as rutile needles - add value. Rutile needles cause the "silky shine" effect for which many rubies are prized.
Rubies are often shaped in a mixed cut, which have step-cut pavilions and a brilliant-cut crown. However, rubies perform well in other shapes.
Finding a high-quality ruby over one carat in weight is incredibly rare. Gems that are that large are very expensive.