African rubies from Tanzania usually have a tint or undertone of brown or orange, which makes them also much cheaper than the Burmese reds, but depending upon the precise shade, often more valuable than the Thai ruby, depending on the lather’s color. Rubies from newly discovered deposits in Kenya, Cambodia, Vietnam, and parts of China are very close in hue and tone to Burmese, and may also retain their color in all light. These stones can command very high prices if other quality factors are fine.
Ceylon, rubies are also encountered with relative frequency. However, these are usually so pale that in the United States they would called “pink sapphire” rather than ruby since the tone is consistently so light. The saturation of color is too weak to be technically described as ruby, since ruby should be red, not pink. You should be aware that in the United States, the color must be deep enough to be considered red to be called “ruby” while in other parts of the world, the name “ruby” may be applied if the stone falls anywhere in the pink to red range. It should be noted that sapphire and ruby are the same stone, physically and chemically. The red variety is called ruby, while the equally popular blue is called sapphire. Both belong to the “corundum” family.
Next, let’s look at the spectrum of emerald colors. Some of the finest emeralds today come from Colombia and are the color of fresh, young green grass; an almost pure spectrum green with a faint tint of either yellow or blue. The color found in the finest of these emeralds is unique to Colombia. Unfortunately, very fine Colombian emeralds with exceptional color are extremely rare now, and thus very costly.
African emeralds can also exhibit a lovely shade of green, but with a bluer undertone, and a slightly dark tone, probably due to traces of iron, which may make the stone less desirable, and thus less valuable than a fine emerald from Colombia. However, the African stones usually have fewer inclusions (flaws) than Colombian, and depending on depth of color, compare very favorably to the Colombian, aesthetically, while costing less per carat.
Light and environment affect the color you see
The color of a stone can be drastically affected by the kind of light and the environment in which the examination is being conducted; that is , variables as disparate as the color of wallpaper or the tint of a shirt can alter a stone’s appearance. If examined under fluorescent light, a ruby may not show its fullest red, because most fluorescent lights are weak in red rays; this causes the red in the ruby to be diminished and to appear more as a purple red. The same ruby examined in sunlight or incandescent light (an ordinary electric light bulb), neither of which is weak in red rays, will appear a truer, fuller red. Because the color of a ruby is dependent upon the “color temperature” or type of light used, it will always look best in warm light. A ruby looks even redder if examined against a piece of orange yellow paper. For this reason, loose rubies are often shown in little envelopes, called “parcel papers,” that have a yellow orange inner paper liner to show the red color to the fullest.
Blue sapphire, another intensely colored gem, comes in numerous tones of blue; from light to very dark, some so dark that they look black in incandescent (warm) light. gemtv Most sapphires, however, look bluest in fluorescent light, or day light. Many contain some degree of green. The more green, the lower the price. Some even exhibit a change; we’ve seen blue sapphires that were a magnificent blue in daylight turn to an amethyst purple in incandescent light. Some, like the stones from the Umba Valley in Tanzania, turn slightly lavender over time. The lighter blues are generally referred to as Ceylon colored sapphire; the finest and most expensive blue sapphires generally come from Burma (now called Myanmar) and Kashmir and exhibit a rich, true blue in all kinds of light. Those from Kashmir exhibit a more subdued, soft velvety look comparison to Burmese or Ceylon types sapphires.
An environment that is beneficial to your gemstone can also be created by the setting in which the stone is mounted. For example, an emerald cut emerald mounted in a normal four prong setting will not appear to have as deep a color as it will if mounted in a special box type setting that completely encloses the stone so that light is prevented from entering its sides. The “shadowing” effect created by this prevented from entering its sides. The “shadowing” effect created by this type of enclosure deepens the color of the stone. This technique, and other types of special mounting, can be used to improve the color of any colored gemstone where it is desirable to intensify the color.
Another example is found with a fine expensive imperial jade. A fine jade cabochon (a smooth, rounded cut which has no facets) is often mounted with a solid rim around the girdle (bezel set), with the back of the ring constructed much deeper than the actual bottom of the stone, and the back side of the ring nearly completely closed except for a small opening at the bottom center. This is done either to hide a stone’s defect or to improve its body color.
Opal, too, is often set in ways that enhance color. The environment in this case is a closed, flat backing which has been blackened to intensify the play of color (fire) seen in the stone.
A word about color distribution or zoning
Even though zoning doesn’t really describe color, and is sometimes evaluated as part of the “clarity” grade, we think it should be discussed as part of color evaluation.
In some stones the color is not always evenly distributed but exists in zones; in some stones the pattern created by altering ones of color and colorlessness resembles stripes. Zoning is frequently observed in amethyst, ruby, and sapphire. These zones are most easily seen if you look through the side of the stone and move it slowly, while tilting and rotating it.