Chemical Sensitivity in Gems: What Damages Your Stones and How to Prevent It

Diamonds dissolve in hydrofluoric acid. Pearls are slowly destroyed by the natural acidity of human perspiration. Emeralds lose their fracture-filling treatment in alcohol or acetone. Turquoise discolours on contact with cosmetics. The chemical world is full of hazards for gemstones — and many of them are hiding in plain sight in customers’ daily routines: perfume, hand cream, cleaning products, swimming pool chlorine, and even the mild acidity of sweat. Chemical sensitivity is the least visible of the three components of gem stability, but it is responsible for a significant proportion of the damage that fine jewellery sustains over time.

This article maps the chemical vulnerabilities of the most important gem species and provides practical guidance on how to protect stones from chemical damage in both professional and customer care contexts.

How Chemicals Damage Gemstones

Chemical damage to gemstones occurs through several mechanisms:

Dissolution and Etching

Acids attack carbonate-based gems (pearls, coral, calcite) by reacting with the calcium carbonate that forms their structure. The reaction is: calcium carbonate + acid → calcium salt + water + carbon dioxide. Even mild acids — lemon juice, carbonated water, vinegar, the lactic acid in perspiration — can slowly dissolve pearl nacre and etch coral. Strong acids attack a wider range of gems. Fluorite dissolves in hydrofluoric acid. Even diamond’s surface can be slowly etched by strong oxidising acids at high temperatures.

Discolouration and Staining

Porous or absorbent gemstones — turquoise, lapis lazuli, coral, malachite, and some organic gems — can absorb coloured chemicals, cosmetics, and oils, leading to permanent discolouration. Light-coloured turquoise may turn green-grey from absorbed oils; pale lapis may darken unevenly from absorbed cleaning products. These changes are often irreversible.

Fill Degradation

Treated gemstones are often more chemically sensitive than untreated ones because the treatment media have their own chemical vulnerabilities. Cedar oil in fracture-filled emeralds is soluble in alcohol, acetone, and petroleum-based solvents — which are found in many cleaning products, nail polish remover, and some adhesives. Exposure to these chemicals removes the oil from the fractures, making them visible again and potentially altering the stone’s appearance significantly. Glass-filled rubies can be damaged by acidic cleaning solutions.

Surface Degradation

Some gems develop surface damage from repeated contact with specific chemicals. Tanzanite’s surface polish can be damaged by acidic pickle solutions used in metalworking. Malachite and azurite are copper carbonate minerals that react with acids. Some garnets develop a dull surface patina from prolonged contact with certain cleaning chemicals.

Chemical Sensitivity Profiles of Key Species

Pearl

Pearl is the most chemically sensitive major gem species. Nacre — the calcium carbonate and protein composite that gives pearls their lustre — is dissolved by acids, damaged by alkalis, attacked by solvents, and degraded by heat. Specific hazards: perfume (apply perfume before putting on pearls, never directly onto pearl surfaces), perspiration (wipe pearls with a soft damp cloth after each wear), cosmetics and hairspray, chlorine (pool water and cleaning products), and ultrasonic cleaners (which can loosen the nacre’s bond with the nucleus). The mnemonic “pearls come last” — put them on last after all cosmetics and perfume are applied — is the single most valuable pearl care instruction.

Emerald (Treated)

Virtually all commercial emeralds are fracture-filled with cedar oil, synthetic resins, or polymers to improve their apparent clarity. Alcohol (including hand sanitiser), acetone, ultrasonic cleaners, steam cleaners, and acidic cleaning solutions can all remove or damage the fill. Cleaning instructions for oiled emeralds: warm water with a mild, oil-free soap, applied with a soft brush; no ultrasonic or steam; no soaking; no solvents. Periodic re-oiling by a qualified gemologist may be appropriate for emeralds whose fill has degraded.

Turquoise and Porous Gems

Turquoise is copper aluminium phosphate — a relatively porous mineral that absorbs oils, cosmetics, and other substances readily. This is actually exploited in the treatment of lower-quality turquoise, which is commonly impregnated with plastic or wax to improve colour and durability. Both natural and treated turquoise should be kept away from perfume, cosmetics, sunscreens, and cleaning products. Never clean turquoise with chemical cleaners; a soft dry cloth or very slightly damp cloth is appropriate.

Coral, Malachite, and Carbonate Gems

All carbonate-based gems — coral, malachite, rhodochrosite, calcite inclusions — are acid-sensitive. Even dilute acetic acid (vinegar) will visibly etch coral and malachite. Pool water (which is treated with chlorine and may be acidic) is destructive. In a jewellery context, these materials should never be cleaned with acidic solutions and should not be worn during swimming.

Amber and Organic Gems

Amber (fossilised tree resin, hardness 2–2.5) is soluble in alcohol, acetone, and petroleum solvents. It is also damaged by hairspray and perfume, which can cause surface cloudiness. Clean amber only with a soft dry cloth or very mild soapy water; rinse thoroughly and dry immediately. Jet and other organic gems have similar vulnerabilities.

Chemicals to Avoid in the Workshop and at Home

A practical reference of chemicals that damage common gem species:

Chlorine bleach: damaging to many metals and most organic gems; avoid completely

Acetone (nail polish remover): dissolves amber, attacks oiled emeralds, damages plastics and some adhesives

Alcohol: removes fracture fill from emeralds; harmful to amber, copal, some organic gems

Acidic pickle solution (used in metalworking): damages tanzanite surface, carbonate gems, and some treated stones

Perfume and hair products: particularly harmful to pearls, turquoise, and coral

Swimming pool chlorine: harmful to pearls, coral, turquoise, and many metal alloys

Household cleaning products: contain a wide variety of potentially harmful chemicals; remove jewellery before cleaning

Key Takeaways

Chemical damage mechanisms: dissolution (acids on carbonates), discolouration (absorption in porous gems), fill degradation (solvents on treated emeralds), and surface attack.

Pearl is the most chemically sensitive major gem: acid perspiration, perfume, cosmetics, and chlorine all damage nacre. “Pearls come last.”

Oiled or resin-filled emeralds are damaged by alcohol, acetone, ultrasonic cleaners, and steam. Clean with mild soap and water only.

Turquoise and other porous gems absorb cosmetics and oils; keep away from all beauty products and chemical cleaners.

Chlorine bleach, acetone, alcohol, and acidic pickle solution are the most commonly encountered workshop and household hazards.

Removing jewellery before cleaning the house, applying cosmetics, swimming, and exercising prevents the majority of chemical damage.