- GEMSTONE INFORMATION -
JUDGING THE VALUE OF A GEMSTONE
A misconception in judging gems is that people assume darker stones are more expensive. Actually, color can be too dark, like sapphires that look more black than blue. The truth is the brighter and more vivid the color the better. You will want to look for a clear, medium-tone, intensely color saturated stone.
Another important factor affecting value is clarity. A clear gemstones with no visible flaws or inclusions is the most valued. Inclusions can range from carbon spots to tiny clear lines, or even a granule of another type of stone. Some gemstone varieties like emerald are very rare without inclusions of some kind and the price will take this into account.
A good cut is something that can add a lot of beauty. A well-cut faceted gemstone reflects light back evenly across its top surface. If the stone is too deep and narrow, areas may appear darker. If it is too shallow, parts of the stone could have “windows” and appear washed out. The best way to judge cut is to look at similar gemstones alongside each other.
FEATURED GEM
PERIDOT
Peridot’s green color with the slight tinge of gold is caused by very fine traces of iron.
Peridot from Arizona is rare in sizes above five carats. The most beautiful examples come from the border area between Pakistan and Afghanistan. However, the peridot as a gemstone can be found in Myanmar (Burma), China, USA, Africa and Australia.
GEM TABLE (alphabetical)
| Mohs Scale of Hardness |
Birthstone Month |
|
|---|---|---|
| ALEXANDRITE | 8.5 | June |
| AMETHYST | 7 | February |
| AQUAMARINE | 7.5-8 | March |
| CITRINE | 7 | November |
| DIAMOND | 10 | April |
| EMERALD | 7.5-8 | May |
| GARNET | 7-7.5 | January |
| OPAL | 5.5-6 | October |
| PEARL | N/A | June |
| PERIDOT | 6.5-7 | August |
| RUBY | 9 | July |
| SAPPHIRE | 9 | September |
| TANZANITE | 6.5-7 | December |
| TOPAZ (precious) | 8 | November |
| TOURMALINE (pink) |
7-7.5 | October |
| ZIRCON | 7.5 | December |
ALEXANDRITE
Alexandrite is the color change gem. In daylight it is a cool bluish mossy green and inside in lamplight it changes to a reddish color with a warm raspberry tone.
You can watch the color change by switching the light source from incandescent to fluorescent.
AMETHYST
Most amethyst gemstones on the market today are heat-treated to produce a deeper color. Heat treating is permanent and these stones will not fade over time.
Leonardo da Vinci believed that amethyst could dissipate evil thoughts and quicken the intelligence. Roman legends proclaimed that wearing amethyst jewelry or drinking from a chalice made from amethyst would prevent intoxication from alcohol.
Brazil is the primary source of amethyst, and Zambia is also a significant source.
AQUAMARINE
Aquamarines are found in a range of blue shades, from the palest pastel to greenish-blue to a deep blue. While the choice of color is largely a matter of taste, the deeper blue gemstones are more rare. Remember that Aquamarine is a pastel gemstone, and while color can be quite intense in larger gemstones, the smaller aquamarines are often less vivid.
Found in Nigeria, Madagascar, Zambia, Pakistan and Mozambique, but most of the gemstones available today come from Brazil.
Many aquamarines are greenish when mined and cut. For those who prefer a purer blue, these gemstones are heated to enhance their blue color permanently.
CITRINE
Citrine is a gem at 7 on the Mohs scale of hardness.
Named from the French word for lemon, "citron" since citrine has a juicy lemon color.
Brazil and Zambia is the primary source of this gemstones.
Brownish varieties are commonly heated and magically turn into the bright yellow or orange colors known as citrine. This enhancement method is permanent and will last for the life of the gemstones.
DIAMOND
Diamond is the only material that measures 10 on the Mohs scale of hardness. They are mined in Africa, Canada and Australia.
The world's largest diamond was the Cullinan, found in South Africa in 1905. It weighed 3,106.75 carats uncut. It was cut into the Great Star of Africa, weighing 530.2 carats, the Lesser Star of Africa, which weighs 317.40 carats, and cut into 104 other diamonds of nearly flawless color and clarity. These gems form part of the British crown jewels.
EMERALD
Mined in Colombia, Brazil and Zambia.
Emeralds from Zimbabwe are among the oldest gemstones anywhere in the world.
It is mainly traces of chromium and vanadium which are responsible for the fascinating color.
Inclusions may make individual gems vulnerable to damage if handled roughly.
GARNET
Garnets range from 7-7.5 on the Mohs Scale of Hardness. The name originates from the ancient Greeks because the color reminded them of the "granatum," or the pomegranate seed.
This gem comes in many colors from the deep red Bohemian Garnet to the vibrant greens of the Russian demantoid and African tsavorite. The oranges and browns of spessartite and hessonite come from Namibia and Sri Lanka. Rhodolite is a mixed crystal of almandine and pyrope garnet. It was originally found in the USA, and now comes mostly from East Africa, India and Sri Lanka.
OPAL
Opals come primarily from Australia and Mexico. Almost ninety-five per cent of all fine opals come from Australia. Dark or Black Opal, White Opal, Crystal Opal, Boulder Opal from Queensland. Also from Queensland are the Yowah Nuts, the so-called “picture stones“. The Mexican stones are called " Fire Opal".
The color play of Opal is caused by small spheres of silica gel with varying percentages of water (between 2 and 6 per cent) that interfere with refraction, and are responsible for the fantastic play of colors. The spheres dissect the light on its way through the gemstone separating it into all the colors of the rainbow.
Lightning Ridge is where coveted Black Opal is found.
The largest Opal found weighing 6,843 kilograms, is called the “Andamooka Desert Flame”.
Coober Peddy is an Aborigine word meaning “white man in a hole“, which describes how Opal is mined.
Opal, should be treated with some care. It is softer than many other gemstones and should be stored carefully to avoid being scratched by other jewelry. It should also be protected from blows because exposed corners can chip. Opal should not be exposed to heat or to acid.
PEARL
Pearl is very soft and is the only gemstone to come from a living creature.The majority of cultured pearls come from Japan, China and the South Pacific.
Pearls are sensitive to chemicals and acids. To care for your cultured pearls, avoid using perfume, hairspray, abrasives, solvents, and nail polish removers while wearing them. Like your skin, cultured pearls contain water and may dehydrate and crack if exposed continuously to arid conditions.
For more information on these and other gemstones I suggest the International Colored Gemstone Association web site at www.gemstone.org. as much of the information given here is from their site.
