Rubies: The "King" of Gemstones
There is rich folklore that surrounds the ruby. Many amazing things have been said to be represented by the ruby. Integrity, devotion, happiness, healing are just some of the properties believed to belong to the ruby. And don't forget romance.
Rubies have a distinct red aura that causes them to seem bigger than they are. Rubies are normally not as large as other gemstones. So a good, well cut ruby can bring a very high price.
Rubies are one of the hardest gemstones, in a class of minerals known as CORUNDUM, a combination of aluminum and oxygen. It is second in hardness to diamonds. And in any color other than those in the red family, will be classified as sapphire. While the red colors of rubies can run from almost orange to slightly purple.
The saturation of color is an important thing to understand if you are considering buying a ruby. Saturation will show the color purity of the stone, and will range from vivid to weak. Vivid is the desirable saturation. The tone of the ruby can go from very dark to very light, with a medium tone being ideal.
When shopping for rubies look for stones with vivid color saturation, without hints of gray or brown. These dark areas of a ruby are known as EXTINCTIONS, and can be effected by tone, cut, and even lighting. The fewer areas of extinction in your ruby, the better! And lighter colored and shallow cut stones will normally show fewer extinctions than the deep darker colors and cuts.
There is no convenient method "set in stone" to characterize or catalog the color of rubies. Rubies have so many variations in tone, color purity, and saturation. So picking the perfect ruby is truely a very personal experience.
The term INCLUSION is used by gemologists to define characteristics found within a stone. Inclusions often indicate that the gemstone is natural. While on the other hand, a BLEMISH is a characteristic that affects the stone's surface. Some common inclusions are:
Crystals, which are solid and in many shapes and sizes. Very small crystals are known as pinpoints or grains.
Silk, which are tiny fine fibers of titanium dioxide, (or other minerals). Well formed silk indicates your ruby has had no heat treatment, and is natural. Silk is a preferred inclusion in a ruby.
Needles, which are longish, thin crystals of gas or liquid filled tubes, (growth tubes).
Cracks, which are fractures or fissures that appear feather like.
Other inclusions also exist.
Rubies are rare enough that gem cutters tend to form the stones into ovals more often than round cuts. This is to avoid waste of the rough stone. Round rubies loose more of the rough, and so are usually more expensive than a oval of the same weight.
Rubies are sometimes treated to effect their beauty. Conventional heat treatment is a typical process for rubies as well as many other gems. This is done to remove haziness from the stone and improve the color. This treatment is many times referred to as an ENHANCEMENT.
One of the side effects of modern heat treatment of corundum is the heating units reach near the melting point for rubies, (2050 degrees C). This evironment may contain borax or alumina powders to even out the temperatures and to prevent heat related cracks.
But... the powders also may fuse in these high temperatures and form a type of melted glass that permeates cracks of fissures on the surface of the stone. These changes can be seen under magnification, because rubies and glass have different refractive indexes.
Flux heat treatment is a relatively new enhancement and goes a step further. This treatment tends to "heal" fractures and fissures. With cracks becoming invisable to the naked eye. Powerful microscopes are needed to detect this treatment process, or the solidified "streams" of melted ruby that "flow" into the cracks durning the extream heating process.
Fissure Filling is a treatment in a class all it's own. A fissure filled ruby will look amazing! But it's value is far below rubies without treatments, or heat treated rubies. Fissure filled rubies usually start with the lowest grade rubies. They are acid washed to cause them to become very porous. Next they are packed in with silica based salts, then heated. In the high heat, the silica salts melt into glass and fill the acid produced pores of the ruby.
This last treatment produces the least expensive, and normally less desirable ruby. But as I said these stones can look amazing. So if you desire a beautiful ruby, but can't afford the cost of a fine natural un-treated stone, or even the a conventional heat treated or flux treated stone, go ahead and buy a fissure filled ruby just for the fabulous look!
I personally own untreated, and fissure filled rubies. I have as much fun with one as the other. And no-one can tell the difference! Both are lovely, and only I know which one was less expensive.
Rubies have been some of the most sought after gemstones in history, and continue to be alluring and romantic. Possibly the oldest gemstone known to man, the fabulous ruby truely is the king of gemstones!