Gem Care and Durability

Diamond, topaz, kunzite, and tanzanite are the four cleavage risks documented in the principal gemstone-durability review used for this table ^[5]. Fluorite and moonstone cleavage are separately sourced from a gemmological reference dictionary ^[10][11], since the durability review does not cover either species.

Beyond cleavage, sharp impacts can chip facet edges and girdles even on tough, non-cleaving gems. Worn or abraded facet edges on older cut diamonds have been documented as a recognisable long-term wear pattern ^[12]. Protective settings reduce this risk for daily-wear rings (see Setting Recommendations below).

Some gems have exceptional toughness despite only moderate hardness:

• Nephrite jade (Mohs 6-6.5): interlocking fibrous amphibole structure gives exceptional toughness relative to its hardness ^[1]
• Jadeite (Mohs 6.5-7): granular interlocking pyroxene structure ^[13]
• Chalcedony (Mohs 7): microcrystalline quartz aggregate

These polycrystalline gems resist chipping better than single-crystal gems of equal or even higher hardness.

Ultrasonic cleaners use high-frequency sound waves to drive cavitation, the rapid formation and collapse of microscopic bubbles in the cleaning solution, which dislodges surface dirt ^[14][15]. The same energy that removes dirt can also:

• Strip or damage fracture-filling oils and resins in emerald ^[4]
• Loosen glass fillers in lead-glass-filled ruby ^[16]
• Dislodge fillers in clarity-enhanced diamonds ^[17]
• Propagate existing fractures in gems with pronounced cleavage
• Damage organic gems such as pearl and amber

Steam cleaning combines heat and moisture and is a documented risk for oiled or resin-filled emerald ^[4][18], lead-glass-filled ruby ^[16], filled diamonds ^[17], and opal, where rapid temperature change can encourage crazing ^[19].

Kunzite, the pink-to-lilac variety of spodumene, owes its colour to manganese-related colour centres that are documented to bleach under prolonged strong light or heat ^[34][35]. GIA's consumer guidance confirms the practical consequence: kunzite can fade with extended exposure to heat or intense light ^[33]. Store kunzite away from strong light and heat, and out of direct sun in a display case.

Some amethyst colour can fade with prolonged exposure to intense light ^[31]. This is a separate phenomenon from the well-studied heat- and irradiation-induced colour change between the amethyst and citrine forms of quartz, driven by iron-related colour centres ^[36][37]. Amethyst should be kept away both from strong display lighting and from direct heat.

Rose quartz's colour stability under normal wear is not well documented in the scientific literature; as a precaution, avoid prolonged direct sun exposure and very hot conditions.

Natural brown topaz can lose colour on exposure to light and heat, a phenomenon documented in early studies of colour alteration in topaz ^[38]; heat can also visibly alter mineral inclusions within topaz ^[39]. Irradiated blue topaz, the most common topaz colour on the market, is considered stable under normal wear and light exposure, though as with any colour-treated stone it should still be kept away from prolonged high heat during repairs (see Treatment-Specific Care below).

Deep blue "Maxixe" and Maxixe-type beryl owes its saturated colour to unstable radiation-induced colour centres and is strongly documented to fade on exposure to light, in some cases within weeks of display ^[40][41]. This material should be stored in the dark and treated as display-only.

Opal is an amorphous, hydrous form of silica whose water content contributes to crazing, a network of fine internal cracks ^[2]. Controlled heating experiments show that opal stored in water cracks at markedly lower temperatures once it later dries out than opal stored in air, and that for water-stored material the cracking is linked to drying shrinkage rather than superheated-water decrepitation ^[19]. In practice this means water storage does not protect opal from crazing and may make it more vulnerable once it is removed from water (see Storage Guidelines below).

Heat measurably changes tanzanite's colour: laboratory heat treatment shifts natural brownish, trichroic material toward the pure violet-to-blue dichroism seen in most commercial stones, an effect attributed to vanadium as the principal colouring agent ^[42][43]. This colour sensitivity is distinct from the risk of physical fracture: tanzanite's perfect cleavage makes sudden temperature change a plausible mechanical hazard, though this specific fracture mechanism has not been directly studied. As a precaution, avoid sudden temperature swings and never use ultrasonic or steam cleaning ^[25]. General thermal behaviour of the zoisite mineral group provides supporting background ^[44].

Turquoise and chrysoprase are both sometimes reported to dull or dehydrate with age and exposure to heat or dry air, but this is not well documented in peer-reviewed gemmological literature. [CITATION NEEDED] Keep both away from direct heat as a precaution, and see Chemicals, Cosmetics and Metal Care below for turquoise's separately well-documented chemical sensitivity.

Pearl nacre can be damaged by many chemicals and all acids, including hair spray, perfume, cosmetics, and even perspiration ^[3]. Trade practice accordingly recommends putting pearls on last, after cosmetics and perfume have been applied, and taking them off first; this sequencing is standard trade practice rather than a documented finding in its own right, but it follows directly from pearls' well-documented chemical sensitivity ^[3]. Wipe pearls with a soft cloth after wearing; never clean them ultrasonically or with steam.

Chloride ions are documented in laboratory testing to cause stress-corrosion cracking in low-karat gold alloys ^[45][46][47]. Chlorinated pool and spa water is a chloride source, so although these specific studies tested laboratory salt solutions rather than pool water directly, extending their finding to swimming and hot-tub use is a reasonable precaution: remove gold jewellery before swimming in chlorinated water.

Turquoise is porous and can be discoloured by skin oils, cosmetics, and other chemicals, and dissolves slowly in hydrochloric acid ^[27]. Some commercial turquoise is treated to reduce this porosity and its tendency to absorb discolouring agents ^[48]. Clean turquoise with a soft, slightly damp cloth only, never with solvents or ultrasonic cleaning.

Coral is a calcium-carbonate skeletal material ^[49] and malachite is a copper carbonate mineral ^[50]; both are attacked by acids, including many common household and cosmetic products, and both scratch and etch easily. Clean both with a soft dry cloth only.

Amber can be damaged by many chemicals, including perfume, hairspray, and cleaning solvents, and the only safe cleaning method is warm soapy water ^[51]. Amber's solubility in organic solvents is well enough established that solvent treatment is itself used as an analytical technique to recover fossil pollen and spores trapped inside it ^[52], illustrating how reactive the surface is.

Lapis lazuli is often dyed to even out its colour, and this dye can be removed by acetone or denatured alcohol; the wax sometimes used to seal the surface can also deteriorate with heat or solvents ^[53]. Test any cleaning method on an inconspicuous area first, and avoid solvents and prolonged heat.

Recommended for prong settings (rings): Diamond, ruby, sapphire, chrysoberyl, spinel

Recommend bezel or other protective settings: Emerald, tanzanite, opal, moonstone, tourmaline, peridot

Best avoided in daily-wear rings: Kunzite, fluorite, pearl (unless in a protective setting)

• Store gems individually, in separate soft pouches or fabric-lined compartments, not loose together
• A diamond can scratch any other gem material, and can also scratch the precious metal of another piece's setting ^[20]
• Softer gems should never share a compartment with harder ones

• Store light-fading gems, kunzite, amethyst, brown topaz, and Maxixe-type beryl, away from strong or prolonged light ^[33][31][29]
• Avoid extreme or fluctuating temperatures; stable room temperature and humidity suit most gems best

Do not store opal in water or on damp cotton wool, despite this being long-standing trade advice. Peer-reviewed testing shows that water-saturated opal actually cracks at lower temperatures once it later dries ^[19], so wetting opal relocates rather than removes the crazing risk. Only certain Ethiopian hydrophane opal varieties genuinely absorb and release water reversibly without damage ^[54], and these should be identified by a gemmologist rather than assumed. Ordinary precious opal should be stored dry, away from extreme heat and rapid temperature change, and not sealed in an airtight container.

Dry strung pearls fully before wearing or storing them, since damp string encourages stretching and mildew ^[3]. Store pearls flat, away from harder gems that could scratch the nacre.

Nearly all commercial emerald is fracture-filled with oil or resin (traditionally cedarwood oil, more recently synthetic resins such as Opticon) to reduce the visibility of surface-reaching fractures ^[4][55]. A dedicated durability study of 128 filled emeralds found that around 35% changed detectably after mild exposure testing, with liquid oil fillers the most susceptible to ultrasonic cleaning and to solvents such as ethanol and acetone; the study recommends cleaning with soap and water only, and professional re-oiling or resealing when a filler visibly degrades ^[18]. Never use ultrasonic or steam cleaning, and keep filled emeralds away from a jeweller's torch and other high-heat repair work ^[56].

Ruby with large fractures is increasingly filled with high-lead-content glass, a treatment classed by consumer-protection regulators as producing a composite stone rather than ruby (see treatment disclosure). Lead-glass filling is markedly less durable than traditional oil or resin filling in emerald: the glass filler can be attacked by common household chemicals, dissolved by lemon juice and other mild acids, and can even melt under the heat of a jeweller's torch during routine repair work ^[16]. Clean lead-glass-filled ruby with a soft cloth and mild soap only; never use ultrasonic or steam cleaning, and warn a repair jeweller before any torch work.

Diamonds with fractures reaching the surface are sometimes filled with a high-refractive-index glass to make the fracture less visible. The filler is documented to be vulnerable to the heat of jewellery repair, to ultrasonic cleaning, and to some jewellery-cleaning chemicals, and can visibly change or become dislodged as a result ^[57][17]. Clean filled diamonds with a soft cloth and mild soap only, and inform any jeweller carrying out repairs or resizing that the stone is filled.

Heat treatment is the most widely accepted enhancement in the ruby and sapphire trade, and heat-treated stones are generally considered as durable as untreated stones for normal wear, cleaning, and repair ^[58][21][22]. Some yellow sapphire colour types are more light- or heat-sensitive than others depending on their colour origin ^[59], so care recommendations can vary by colour type. Beryllium-diffused corundum is the exception to the "no special care" rule: the diffused colour layer is extremely thin, and repolishing or recutting facets on a beryllium-diffused stone can remove the colour layer entirely ^[58].

Dyed gem materials, including dyed chalcedony, jade, and pearls, are reviewed in the gemmological literature primarily as an identification challenge ^[60]. Whether the dye itself fades under normal light exposure is not well documented for most dyed materials. [CITATION NEEDED] As a precaution, clean dyed gems with a soft cloth and mild soap only, avoid solvents, and keep them out of prolonged strong light.

Surface coatings, used for example to enhance the blue-violet colour of some tanzanite, sit on the surface of the stone rather than penetrating it, and can be scratched, worn away by everyday abrasion, or removed by solvents and ultrasonic cleaning ^[61][60]. Clean coated stones with a soft dry cloth only, and treat any coating as cosmetic and temporary rather than permanent.

Irradiated blue topaz is considered colour-stable under normal wear and light exposure once appropriately treated and settled to safe radioactivity levels; the main care concern is the same cleavage-related caution that applies to all topaz (see Toughness and Cleavage above). High-pressure high-temperature (HPHT) treatment of diamond is reported to produce a permanent colour change under normal conditions, though the original studies establishing this are not independently retrievable, so the claim rests on secondary review rather than a directly checkable primary source ^[60]. As with any treated diamond, avoid unnecessary exposure to extreme heat during repair work.