Diamond. Adamas, the invincible; the unconquerable. The hardest substance on earth. Ice. Transparent carbon, without color, and without rival.

Grade them D, E, or F, and you have a colorless diamond. These are the top grades in the Gemological Institute of America diamond grading scale. (No, there is no A, B, or C grade.) Colorless diamonds are transparent, and by definition have no visible color in the face-up position. Near-colorless diamonds have no visible color face up but do have a very slight suggestion of color—yellow, brown, or gray—visible through the pavilion. These stones are given the letter grades G, H, I, or J.

Colorless and near-colorless diamonds are rare. Mother Nature will more often grow diamonds with impurities that add visible tints of yellow, brown, or gray. And in fact, diamonds can grow in all the hues of the rainbow, as well as black and white. That makes for quite an eyebrow-raiser when you consider that numerous diamond dealers traditionally label colorless or near-colorless diamonds “white diamonds.” (See “Color” below.)

History and romance. Diamond history begins in India. Many important colorless diamonds came from the south central Golconda district, where they were first mined from about the fourth century BCE. This region extended south and east through five provinces, with the ancient city of Golconda serving as the central market for distribution and cutting of the gems. The Koh-i-noor, now 105.6 cts. and set in the British Crown Jewels, and the Great Mogul, reportedly a 787-ct. rough crystal, were mined there. Today, when one sees an exceptionally transparent and colorless diamond in an estate jewelry piece, it is likely to be a Golconda stone.

In 1730, diamonds were discovered in Brazil, and much of what was found was first shipped to India to be sold as Indian in origin. Still a rare jewel, diamonds were worn only by the aristocracy.

Late in the following century, diamonds were discovered in South Africa—and thus began the era of diamonds worn by the masses. Today, there are major diamond fields in Australia, Russia, and Canada, helping to keep the consuming public adorned with diamonds.

Romancing the stone is said to have begun with the Archduke Maximilian of Austria (1459-1519), the first noble to give a diamond engagement ring to his intended, Mary of Burgundy.

The sixth-most-popular slogan of the 20th century, “A Diamond is Forever,” launched the campaign to make the diamond engagement ring a tradition … and it worked. Mary Frances Gerety (1916-1999) created the slogan in 1948 for N.W. Ayers, the marketing firm hired by De Beers, which used the phrase in its global campaign in 1960. In 2001, according to the Diamond Information Center, 84% of U.S. brides received a diamond engagement ring.

Color. Colorless diamonds have no color and are transparent. White diamonds are semitransparent or translucent and white, which is the color of milk and not the same as colorless. But that doesn’t stop the majority of dealers from calling colorless diamonds “white.” Suffice to say that unless you’re talking with a colored-diamond specialist, “white diamonds” are not white.

Colorless diamonds are placed in the Type IIa category of the two diamond types. Type I diamonds have nitrogen impurities, which typically impart a faint- to fancy-yellow color. Type II diamonds either have almost undetectable amounts of impurities (Type IIa) and appear colorless, brown, or pink; or have sufficient amounts of boron (Type IIb) to create gray and blue diamonds.

Pricing. Colorless diamonds are at the top of most pricing charts. The Rapaport Diamond Report pricing guides suggest that a 1-ct. D/VS2 round brilliant should have an asking price of $7,900/ct. The Guide, which also publishes colored-gem prices, usually assigns a more realistic lower-than-Rap value, showing the same D/VS2 at $6,400/ct.

Enhancements. As noted above, Type IIa diamonds can be colorless, light brown, or pink. Browns have been found to react to high pressure and high temperature (HPHT), which manipulate the minute amounts of nitrogen to reduce or eliminate the brown tint. (Brownish pink diamonds also react well to HPHT, which eliminates the brownish component.) Colorless Bellataire diamonds, by Lazare Kaplan, are the premier HPHT-enhanced diamonds in the market. Because natural colorless diamonds are typically Type IIa, the detection of enhanced Type IIa diamonds is still difficult, leading many gem labs to believe that they can identify most, but not all, HPHT diamonds. An inscription on the girdle of every Bellataire diamond identifies it as enhanced.

Care and cleaning. Diamond is the hardest material on earth, but it’s not the toughest. Hardness is resistance to scratching, so you won’t scratch a diamond unless you rub another diamond against it. But you can break it. One good smack against a car door or a turn around the garbage disposal, and you can separate the crystal into two pieces. For small chips and bruises, you can have the diamond recut. For larger fractures, an “all risk” insurance policy is suggested.

The object of cleaning is to remove the grease (dirt, hairspray, hand cream, pie crust, etc.) from the pavilion facets. Anything stuck to the back of the diamond will allow light to “leak” or fall through the back facets, rather than being reflected and bounced up through the crown. Steam cleaning and ultrasonic cleaning are the preferred methods. If a steamer or ultrasonic is unavailable, a toothbrush and a little ammonia detergent will do just fine. Caution: Using bleach will not whiten the diamond, but it will destroy the alloy in a gold mounting.

Bench repair and setting. Clean all diamonds before repairing a piece. The surface of a diamond can be burnt if oil or grease (even from one’s fingers) is left on it while working on diamond jewelry with a torch. Burn marks must be polished off by a professional diamond cutter. Diamonds can be cleaved if they’re struck hard in the octahedral direction, so no hammering, please!

Recommended reading. For more information, see Collecting and Classifying Coloured Diamonds, Stephen C. Hofer, Ashland Press (1998), New York; or “The Golconda ‘D,’ ” Gems & Gemology, Winter 1984, GIA.