Diamond Eduction - 4 C's of Diamonds

Things to know when buying Diamonds, first we'll start with the 4 C's of diamonds (clarity, cut, color, carat) and then finishing with some other diamond facts. For more information and diagrams on the 4 C's of diamonds check out our ebay store diamond page: http://stores.ebay.com/OldCities-Estate-Jewelry/Diamond-Information.html.

THE 4 C's of Diamonds!

Cut - the most important of the 4

Cut refers to the shape of the stone and also gives of the brilliance of the stone. Diamonds can come in all different shapes from round, princess, emerald, pear, etc. You can also find diamonds uncut or rough, these diamonds are older and have much value, but little brilliance or luster. To grade the cut of a diamond you look at the shape of the cut, proportions and symmetry as well as outer marks, these are all taken into consideration. The brilliance of a diamond comes from the underneath table, how many facets there are, how they are cut and how the light hits off of each of those facets, this is what makes the diamond sparkle.

Color - How colorless is the diamond?

Diamond color is hard to judge by the naked eye, most use what is called a loop. Color is graded using the alphabet staring at D (best in color or colorless) all the way down to Z (a yellow diamond). Diamonds also come in what they call fancy colors: green, red, blue, purple and yellow, while also coming in brown and black. These stones are generally graded differently.

Clarity - How clear is the diamond?

Clarity refers to the internal/external flaws or inclusions the diamond has. Clarity starts as LR which is internally flawless or inclusion free when looking through a 10 X magnification, all clarity is judged with some sort of magnifier, never done by the naked eye, the naked eye misses many inclusions. If the stone has very few or minor inclusions it is graded VVS, VS is very small inclusions, going to SI small inclusions, to I distinct inclusions and rounding out at PI very large inclusions. To get the clarity of a diamond the best way to do it would to be to go to your local jeweler and ask.

Carat - How big is the diamond?

Carat weight is determined by the width, height, depth, stone shape and stones specific gravity.

OTHER DIAMOND FACTS:

Chemical composition -- Almost pure carbon, crystallized under extremes of heat and pressure.

Color -- Colorless to yellow, brown, orange, blue, green, pink, black. Most diamonds are slightly yellowish, and in this general color range, those most approaching absolute lack of color are most prized. However, brightly colored diamonds are much rarer and more expensive.

Optics -- R.I. 2.417. Dispersion 0.044 (high).

Durability -- Hardness 10 on Mohs scale. The hardest natural substance. Diamonds can be cut and polished only with other diamonds, and only because of slight directional differences in hardness and a perfect octahedral cleavage. While diamonds are tough, they can be chipped along sharp girdles or facet edges. Diamonds are also highly heat resistant, but they can be burned if subjected to prolonged high heat.

Crystal structure -- Isometric (cubic).

Specific Gravity -- 3.515.

Sources -- The major sources include southern Africa, Australia, and Siberia. In North America, the best known source is at Murfreesboro, Arkansas, although it has not been commercially developed. Significant deposits have been found recently in Canada.

Is your Tanzanite Coated?

A recent article was released about tanzanite, we thought we would share. Rest assured that ALL tanzanite sold at OldCities.com has been tested and is 100% natural and has not been coated. We are merely sharing the article to make you aware of this new process people are using to up the value of a tanzanite.

ARTICLE POSTED MAY 27, 2008
Two gemological labs that specialize in colored-gemstone identification have identified a new, non-permanent type of tanzanite treatment that requires disclosure at the point of sale.

The American Gem Trade Association Gemological Testing Center (AGTA-GTC) and American Gemological Laboratories (AGL) recently received faceted tanzanite samples that were later determined to have been coated.

Evan Caplan of Omi Gems sent samples to several labs after a light repolishing of a few stones resulted in a noticeable loss of color.

"Until now, we had not identified a coating on tanzanite to improve its color," AGTA-GTC Director Lore Kiefert said in a release issued on Friday.

The treatment is not immediately obvious, but careful examination with a microscope and in immersion provided clear indications of the coating in most instances, said Christopher Smith, vice president and chief gemologist of AGL.

"This was evidenced by abrasions along facet junctions and at the culet where the coating had worn off, as well as a subtle iridescence when viewing the surface with reflected light," Smith said.

Advanced analytical testing pinpointed that the coating contained cobalt.

"The most reliable means to substantiate the presence of the coating is the use of X-ray fluorescence spectroscopy," Kiefert said, adding that the cobalt is readily detected through that particular analytical technique.

Although the gemstone industry has become very familiar with the practice of heating tanzanite to achieve the best violet to blue color, the color-enhancing coating on tanzanite has not been seen before.

The majority of the tanzanite sample was composed of smaller calibrated stones. Fine color tanzanite in this size range is rarely sent to a lab and therefore would ordinarily avoid detection unless closely scrutinized.

"This is just another reminder that each and every gemstone should be fully examined to determine whether or not it has been treated," Smith said. "Today, it is not uncommon to see stones that have been treated using multiple or compound techniques to achieve a particular result."

Both Kiefert and Smith emphasized that any treatment used to modify the color of a gem should be disclosed. Coatings, in particular, are not considered permanent and in the United States are required by Federal Trade Commission guidelines to be properly disclosed at the point of sale.