The Chatham emerald is the trade name for hydrothermally and flux-grown emerald produced by Chatham Created Gems of San Francisco, the firm founded by Carroll F. Chatham (1914-1983) and continued under his son Tom Chatham. Although the company today is best known as a producer of laboratory-grown emerald, ruby, sapphire, alexandrite, and yellow sapphire, it was emerald that established the Chatham name, and the term "Chatham emerald" is still used in the trade as shorthand for any high-quality flux-grown emerald, in much the way "Hoover" came to mean any vacuum cleaner. Whether that loose usage is accurate in any given case has to be tested against the actual maker.

Origins of the synthesis

Carroll Chatham began experimenting with emerald growth as a teenager in the early 1930s, working in a basement laboratory in San Francisco. By 1935 he had produced his first sizeable single crystal of synthetic emerald, and by the late 1930s he was offering small cut stones to the trade. His method was a flux-melt process in which beryllium oxide, alumina, and silica were dissolved in a molten flux at high temperature, with chromium added as the colourant, and emerald was allowed to crystallise on a seed plate as the system cooled. The technique placed Chatham among a small handful of mid-twentieth-century pioneers - alongside Pierre Gilson in France and, earlier, IG Farben's Igmerald in Germany - who succeeded in growing emerald in commercially useful sizes.

Gemmological character

Flux-grown Chatham emerald has the same chemical composition and crystal structure as natural emerald: it is genuinely beryl, coloured by chromium, with refractive indices, specific gravity, and hardness within the natural range. What separates it gemmologically is the inclusion suite. Where natural emerald typically shows three-phase inclusions, jagged fingerprints, and mineral guests reflecting its hydrothermal-pegmatite origin, flux-grown Chatham material characteristically shows wispy veil-like flux feathers, twisted hollow tubes, and occasional residual platinum platelets from the crucible. Under long-wave ultraviolet light the synthetic typically fluoresces a stronger red than most natural emerald, although Colombian material can also show appreciable red fluorescence, so this test is suggestive rather than diagnostic. Trace-element chemistry, particularly low iron and characteristic ratios of alkalis, gives a more secure separation, and modern laboratory reports from GIA, Gübelin, and SSEF identify Chatham material reliably.

Disclosure and trade reception

From the outset Chatham was unusually scrupulous about disclosure, a posture that distinguished the firm from some of its mid-century contemporaries. The stones were sold as "Chatham created emerald" and the company actively promoted the term "created" rather than "synthetic", arguing that the product was a genuine emerald in every material respect, distinguished only by its place of formation. The Federal Trade Commission's Jewelry Guides have since codified the disclosure requirements, and current GIA practice describes such material as "laboratory-grown emerald" with the manufacturer noted where known.

Place in the contemporary market

Chatham-grown emerald continues to occupy a recognised niche in the jewellery trade, valued at a fraction of fine natural emerald but offering eye-clean clarity and saturated chromium colour at sizes that would be either impossible or prohibitively costly in natural material. The firm has expanded into other species, but the original product remains in production, and the secondary market for older Chatham stones, often set in mid-century pieces, is itself well established. Within the encyclopedia of synthesis, Chatham's contribution is that he showed flux-grown emerald could be produced reliably enough to support a continuous business, and that doing so honestly - with the synthetic origin disclosed at every stage - was compatible with commercial success.