GIA Gem Cleaning Chart Gives Retailers Lab-Backed Care Guidelines by Stone

Most jewelry doesn't lose its sparkle because it's old. It loses its sparkle because someone ran a tanzanite ring through an ultrasonic cleaner without knowing that zoisite, rated poor to fair in stability and clocking in at just 6 to 7 on the Mohs scale, cannot tolerate thermal shock. The GIA Gem Cleaning and Display Chart exists precisely to prevent that mistake, providing concise, lab-backed recommendations for cleaning, display, and care organized by gemstone category.

The chart groups stones by their real-world vulnerabilities: heat sensitivity, solvent exposure, ultrasonic risk. Each entry reflects the gem's actual physical properties rather than generalized advice. Zircon, for instance, carries a hardness range of 6 to 7.5 and earns a "poor to fair" stability rating when heat-treated, improving to "fair to good" in its untreated form. The chart flags a specific behavior worth knowing: some heat-treated zircons revert to their original color when exposed to light, a characteristic with direct implications for display cases and window merchandising.

Zoisite, sold almost universally under its trade name tanzanite, lands at 6 to 7 in hardness and a flat "poor to fair" in stability. Its vulnerabilities include heat, occasional coating treatments, and fracture-filling. The chart's instruction is direct: avoid thermal shock. For a stone that routinely sells at premium prices and sits in prong settings that leave the pavilion exposed to cleaning equipment, that guidance is not a footnote.

Porous gems carry their own separate flag. Skin oils, lotions, and perfumes can discolor them in ordinary handling, which shifts the care burden from the cleaning counter to the sales counter, where a retailer's first conversation with a customer becomes the most important one.

GIA is explicit about the chart's scope. "The information on this chart is intended to provide general guidelines for routine cleaning," the document states. "Outcomes can vary significantly depending on the manufacturer of your equipment; the type and strength of the solutions you use; and the intensity and frequency of their applications. Be sure to follow manufacturer guidelines and, if you're uncertain, avoid steam or ultrasonic." For retailers whose staff may rotate frequently or whose equipment varies by location, that caveat is the operative sentence. Extended care and cleaning information for the gems covered in the chart can be found in the GIA Gem Encyclopedia at GIA.edu.

The chart is downloadable through GIA's Retailer Support Program, a suite of tools built around customer education on the 4Cs, diamond grading reports, and gemstone knowledge. The program includes a 4Cs Counter Display, a 4Cs Brochure available in 18 languages, in-store tools and window displays signaling that a store carries GIA-graded diamonds, and a library of free digital tools: videos on diamond selection, interactive 4Cs scales, and GIA images and logos cleared for use on retail websites. Retailers can register for the Retailer Lookup, download the 4Cs app, and access the full materials library at retailer.GIA.edu.

Gem imagery used by GIA in related materials is credited to Bear Essentials, Bill Larson, David A. Brackna, De Beers, the Dr. E. J. Gübelin Collection, Pala International, Nomad's Co., and Steve Walters — a roster that reads like a cross-section of the serious trade, from private collectors to major mining interests.

The cleaning chart doesn't replace a gemologist's judgment, but it does give every person behind a jewelry counter a defensible, institution-backed starting point before they touch a customer's stone.