An ammonia-based cleaner, in the context of jewellery care, is a dilute aqueous solution of ammonia — typically in concentrations of five to ten per cent — used to dissolve grease, oils, and accumulated grime from the surfaces of durable gemstones and their settings. Commercially sold as jewellery dip or jewellery cleaning solution, such products are effective precisely because ammonia is an alkaline solvent capable of cutting through the sebaceous residues that dull a stone's brilliance. Their use, however, is strictly conditional on the nature of the gem in question: applied to the wrong material, ammonia can cause irreversible damage.

How It Works

Ammonia (NH₃) in dilute solution raises the pH of the cleaning liquid, saponifying fatty deposits and loosening particulate matter lodged beneath settings or within facet junctions. The solution is typically applied by brief immersion — rarely more than thirty seconds to a minute — followed by gentle agitation with a soft brush and thorough rinsing in clean water. The alkaline environment is hostile to organic compounds, which is precisely what makes it effective against skin oils and cosmetic residues, and precisely what makes it dangerous to organic or treated gems.

Gemstones Suitable for Ammonia Cleaning

Ammonia-based cleaners are considered safe for a relatively narrow group of robust, non-porous, untreated stones:

• Diamond — chemically inert and entirely unaffected by dilute ammonia; the combination of ammonia and a soft toothbrush remains a widely used home-cleaning method for diamond jewellery.
• Corundum (untreated sapphire and ruby) — hardness 9 on the Mohs scale, non-porous, and chemically stable; ammonia presents no risk to the stone itself, though heat-treated stones with surface-reaching fractures may be more vulnerable if those fractures have been filled.
• Chrysoberyl and spinel — similarly hard, dense, and non-porous; generally tolerant of dilute ammonia.
• Most unfilled, untreated garnets and tourmalines — though caution is warranted with heavily included or fractured material.

The operative qualifiers throughout are untreated and non-porous. A stone that passes both tests is generally a candidate; one that fails either is not.

Gemstones That Must Never Be Cleaned with Ammonia

The list of contraindicated gems is considerably longer, and the consequences of misuse range from dulling to outright destruction of the stone's surface or internal integrity:

• Pearl and coral — composed largely of calcium carbonate and organic conchiolin, pearls are acutely sensitive to alkaline solutions. Ammonia dissolves nacre, stripping the very layers that give a pearl its lustre. Even brief exposure can cause permanent surface erosion.
• Emerald — the vast majority of emeralds on the market are clarity-enhanced with resins, oils, or wax (most commonly cedarwood oil or synthetic resins). Ammonia attacks these fillers, drawing them out of fractures and leaving the stone visibly more included and duller than before treatment.
• Opal — a hydrated silica with a water content of three to twenty-one per cent; ammonia can disrupt the internal moisture balance and may cause crazing or surface damage, particularly in doublets and triplets where adhesive layers are present.
• Turquoise — porous and frequently stabilised with resins or wax; ammonia penetrates the surface and can bleach colour or dissolve stabilising agents.
• Lapis lazuli — a rock composed of multiple minerals including calcite and pyrite alongside lazurite; ammonia can attack the calcite component and may affect dyed or wax-impregnated material.
• Malachite, azurite, and other carbonates — alkaline solutions react with carbonate minerals directly.
• Amber, jet, and other organic materials — chemically vulnerable to solvents of any kind.
• Any stone with fracture-filling, resin impregnation, or surface coating — regardless of the host species, these treatments are compromised by ammonia exposure.

Considerations for Metal Settings

Beyond the gem itself, the setting material warrants attention. Prolonged or repeated ammonia exposure can accelerate tarnishing in sterling silver and may, over time, stress certain adhesive settings. Plated metals are particularly vulnerable, as ammonia can lift or mottle thin plating layers. Solid gold and platinum are unaffected by dilute ammonia at room temperature, but any setting incorporating adhesive — notably bezel-set stones in some contemporary designs — should be treated with caution.

Best Practice and Professional Guidance

GIA recommends warm water with a small amount of mild dish soap as the safest universal cleaning agent for jewellery, precisely because it poses minimal risk across the broadest range of gem materials. Ammonia-based products, while effective for appropriate stones, should be regarded as a specialist tool rather than a general-purpose cleaner. When in doubt — particularly with antique pieces, stones of uncertain treatment status, or composite gems — the prudent course is to consult a qualified gemmologist or return the piece to a professional jeweller for cleaning. Ultrasonic and steam cleaners carry their own contraindication lists and are similarly unsuitable for universal use.

For collectors and jewellery owners, the single most important habit is to identify every stone in a piece before selecting any cleaning method. A jewellery box containing diamonds, pearls, and an emerald ring requires three different cleaning approaches — and the ammonia solution appropriate for the diamond is among the worst choices for the other two.

Further Reading

• GIA — Gem Care
• AGTA — Gemstone Care and Cleaning Guide