A gem's durability is its ability to survive wear without scratching, chipping, breaking or changing color. Gemologists break it into three parts: hardness (resistance to scratching), toughness (resistance to breaking and chipping) and stability (resistance to heat, light and chemicals). A stone can score well on one and poorly on another, so all three matter when choosing a gem for a ring you plan to wear every day.
Hardness
Hardness is resistance to scratching, usually given on the Mohs scale. The figure that matters most in jewelry is 7, the hardness of quartz. Dust contains quartz grains, so stones below 7 slowly lose their polish and pick up fine scratches. Stones at 7 and above hold a crisp polish far longer.
Hardness also affects how gems interact with each other. A diamond or sapphire stored loose with softer stones will scratch them. Keep pieces in separate pouches or compartments.
Toughness
Toughness is resistance to breaking, chipping and cracking. It is a separate property from hardness, and it is harder to put a number on. Gemologists grade it in words, from exceptional to poor.
Toughness depends on the internal structure of the stone. Jadeite and nephrite are made of tightly interlocked crystals or fibers, and they are among the toughest natural gem materials despite a hardness of only 6 to 7. Jade was carved into axes and tools long before it became jewelry. Corundum has no cleavage and rates as excellent, which is part of why sapphire and ruby wear so well.
Several things reduce toughness:
- Cleavage. Diamond, topaz, kunzite and tanzanite can split along cleavage planes with a sharp blow. The cleavage page explains why.
- Fractures and inclusions. An existing crack gives a new break a head start, and large inclusions can create internal stress. Emeralds, which are often heavily included, are more fragile than their hardness suggests.
- Brittleness. Zircon is hard enough at 6.5 to 7.5, but its facet edges chip easily, so old zircons often show worn edges.
Stability
Stability is resistance to change from heat, light, chemicals and moisture. Several gems are hard and tough enough for daily wear but still vulnerable here.
- Heat. Sudden temperature changes can crack stones with inclusions or cleavage, such as tanzanite and emerald. A jeweler's torch can damage many treatments, and some gems change color when heated.
- Light. Kunzite and some topaz can fade in strong sunlight. Some amethyst can lighten after very long exposure. Irradiated colors in some gems can be unstable.
- Chemicals. Pearls, opal, turquoise, coral and malachite can be damaged by acids, cosmetics, perfume and household cleaners. Lead-glass filled rubies can be etched by mild acids.
- Moisture. Some opal, especially some hydrophane Ethiopian material, takes up water and can temporarily change appearance. Some opals craze, developing a network of fine cracks, as they lose water.
Treatments can lower stability. Oils in emerald dry out or can be removed by solvents, dyes can fade, and coatings wear off. The gemstone treatments page explains which treatments are stable and which need care.
Wearability table
This table gives a general guide. Individual stones vary with inclusions, treatments and cut.
| Gem | Mohs | Toughness | Stability notes | Daily ring wear |
|---|---|---|---|---|
| Diamond | 10 | Good (cleavage) | Stable | Yes |
| Ruby and sapphire | 9 | Excellent | Stable unless glass-filled | Yes |
| Chrysoberyl and alexandrite | 8.5 | Excellent | Stable | Yes |
| Spinel | 8 | Good | Stable | Yes |
| Topaz | 8 | Poor (perfect cleavage) | Some colors may fade | With protective setting |
| Aquamarine | 7.5-8 | Good | Stable | Yes |
| Emerald | 7.5-8 | Poor to fair | Oils and resins sensitive to heat and solvents | With care |
| Tourmaline | 7-7.5 | Fair | Stable | Yes, with care |
| Quartz (amethyst, citrine) | 7 | Good | Some amethyst may fade | Yes |
| Garnet | 6.5-7.5 | Fair to good | Stable | Yes, with care |
| Jade (jadeite, nephrite) | 6-7 | Exceptional | Stable unless dyed or polymer-filled | Yes |
| Peridot | 6.5-7 | Fair | Sensitive to acids and heat | With care |
| Zircon | 6.5-7.5 | Poor (brittle edges) | Some heated colors may revert | With protective setting |
| Tanzanite | 6-7 | Poor (cleavage) | Sensitive to heat shock | With protective setting |
| Moonstone | 6-6.5 | Poor (cleavage) | Stable | Occasional wear |
| Opal | 5.5-6.5 | Poor to fair | Sensitive to heat, dryness, chemicals | Occasional wear |
| Turquoise | 5-6 | Fair | Porous, absorbs oils and chemicals | Occasional wear |
| Pearl | 2.5-4.5 | Fair to good | Sensitive to acids, cosmetics, drying | Occasional wear |
| Amber | 2-2.5 | Poor | Sensitive to heat, solvents | Occasional wear |
Choosing jewelry by gem
Rings take the most abuse. Hands knock against desks, door frames, car doors and kitchen counters, and rings come into contact with soap, lotions and cleaners. For daily engagement or wedding rings, gems with hardness of 8 or more and good toughness work best: diamond, ruby, sapphire, chrysoberyl and spinel.
Softer or more fragile stones can still go in rings worn less often, or in protective settings. A bezel covers the edge of the stone, and a low profile setting keeps it from catching on things. The gemstone settings page compares common styles.
Earrings and pendants see far less impact, so gems such as opal, moonstone, tanzanite and pearls are safer there. Bracelets fall in between, since wrists also knock against tables and doors.
Brooches and pins take the least wear of all and can carry the most delicate materials.
Caring for less durable gems
A few habits help every stone last longer:
- Take rings off for gardening, gym work, cleaning and cooking.
- Put jewelry on after lotions, perfume and hairspray.
- Store pieces separately so harder gems do not scratch softer ones.
- Clean most gems with warm water, mild soap and a soft brush. Avoid ultrasonic cleaners and steam for stones with cleavage, fractures, fillings or porous surfaces.
- Have a jeweler check prongs and settings once or twice a year.
The guide to cleaning jewelry safely lists which gems tolerate which cleaning methods.
Frequently asked questions
What is the most durable gemstone for an engagement ring?
Diamond, ruby and sapphire are the most common choices because they combine high hardness with good to excellent toughness. Chrysoberyl and spinel are also durable options.
Is jade durable even though it is only Mohs 6 to 7?
Yes. Jade is exceptionally tough because of its interlocking crystal structure, so it resists breaking very well. It can still pick up fine scratches over time.
Which gems should avoid ultrasonic cleaners?
Emerald, opal, pearl, tanzanite, turquoise, lapis lazuli, amber and any fracture-filled or coated stone. Gems with feathers or cleavage cracks are also at risk.
Can sunlight fade gemstones?
Some gems can fade in long exposure to strong light. Kunzite, some amethyst and certain irradiated stones are the best known examples.