GIA reset diamond grading by starting at D

By the 1930s, American jewelers described diamond color with a chaos of self-invented, self-interested terms: some used "A," "AA" and "AAA" for their best stones, with no agreement between firms on what any of those meant; others used Roman or Arabic numerals; still others used purely descriptive phrases like "gem blue" or "blue white." A buyer had no way to compare a stone graded "AA" at one shop against one called "blue white" at another, and every grading label had been invented and applied by the same party trying to sell the stone.

Robert Shipley, a former Wichita jeweler who founded the Gemological Institute of America in 1931 after his own gemological ignorance had cost him sales, spent two decades building the professional infrastructure — a school, a research lab, a trade journal — to fix that.

Started the scale at D, a letter no jeweler had ever used and one that signals a poor grade in school, so the top grade could only mean what GIA defined it to mean.

Existing labels like A or AA carried years of inflated claims, so reusing them would inherit distrust.

D had no prior use in diamond grading, so its meaning came entirely from GIA's definition.

The letter D normally signals failure, preventing any assumption of top quality from prior associations.

A clean label made the scale portable and consistent across retailers and countries.

When launching a credential into a market where existing labels are inflated, choose a label with no prior use so its meaning comes solely from your definition.

Because "D" carried no inherited marketing meaning for any retailer to exploit, a GIA "D" grade meant only what GIA had defined it to mean, and the scale became something buyers could genuinely compare across stones and stores rather than one more seller's claim to discount. GIA's D-to-Z color scale, alongside its accompanying cut, clarity and carat weight standards, became — in GIA's own account — the diamond industry's global grading standard, still in universal use worldwide more than seventy years later.