The Complete Gemstone Guide
Written by Mehran, master jeweller and founder of Vanhess. Twelve coloured stones compared honestly — hardness, colour, treatment, daily-wear suitability and relative price — so you choose with your eyes open.
Gemstone Guide: Durability, Colour & Care, Stone by Stone
Key Takeaways
- Three things decide how a gemstone wears: hardness (resists scratches), toughness (resists chips and cracks), and stability (resists heat, light and chemicals). A stone can be hard and still chip easily.
- For an engagement ring you wear every day, aim for a Mohs hardness of 8 or above: sapphire and ruby (9), moissanite (9.25), alexandrite (8.5) and most topaz (8) all qualify. GIA rates corundum (sapphire and ruby) at 9.
- Emerald, opal and pearl are not built for daily ring wear. Emerald is brittle and almost always fracture-filled; opal is soft and sensitive to knocks and temperature; pearl sits around 2.5 on Mohs and scratches with almost anything.
- Most coloured stones are treated in some way. Treatment isn't a dirty word — it's standard — but it should be disclosed, and some treatments are fragile (oiled emerald, dyed stones) while others are permanent (heated sapphire).
- The master table below covers all twelve stones we guide on, with hardness, colour, common treatment, daily-wear verdict and relative price.
How to read a gemstone before you buy
The short answer to "which coloured stone is best for a ring you wear every day" is: pick one that's hard enough not to scratch and tough enough not to chip — for most people that means sapphire, ruby or moissanite. But durability is three separate things, and people mix them up constantly on our bench in Coquitlam.
Hardness, toughness and stability are not the same
Hardness is resistance to scratching, measured on the Mohs scale from 1 (talc) to 10 (diamond). The scale is relative, not linear — diamond at 10 is many times harder than corundum at 9, not 10% harder. Toughness is resistance to chipping and breaking. Stability is how the stone copes with heat, light, and household chemicals. GIA treats all three as separate durability factors, and they don't move together: emerald is fairly hard (7.5–8) but only fair-to-good on toughness, so it chips. A stone that scores well on all three is what you want on a finger that meets door handles, car keys and kitchen counters.
Treatments: standard, but disclose them
Almost every coloured stone on the market has been improved in some way. Heating sapphire and ruby to deepen colour is stable and permanent. Emerald is routinely fracture-filled with oil or resin to hide fissures — that filling can dry out, leak, or be stripped by ultrasonic cleaners and solvents, so an oiled emerald needs gentle care for life. Amethyst is often heat-treated, some topaz is irradiated to turn it blue, and a lot of cheap opal and pearl is dyed. None of this is fraud as long as it's disclosed. Ask, and get it in writing on the receipt.
The master gemstone table
Hardness figures below follow the Mohs scale as published by the International Gem Society and GIA's gem encyclopedia. "Daily-ring suitability" is our bench opinion, weighing toughness and treatment, not hardness alone. Relative price is a rough guide for good commercial quality, not top-tier gems.
| Stone | Mohs hardness | Typical colour | Common treatment | Daily ring? | Relative price |
|---|---|---|---|---|---|
| Moissanite | 9.25 | Near-colourless to faint tint | Lab-grown (no treatment) | Excellent | $ |
| Sapphire | 9 | Blue, also pink, yellow, teal | Heat (stable) | Excellent | $$$ |
| Ruby | 9 | Red | Heat; sometimes glass-filled | Excellent (untreated/heated) | $$$$ |
| Alexandrite | 8.5 | Green in day, red under lamp | Usually none (rare natural) | Very good | $$$$$ |
| Topaz | 8 | Blue, also colourless, pink | Irradiation (blue); stable | Good (chips on edges) | $ |
| Aquamarine | 7.5–8 | Light blue to blue-green | Heat (stable) | Good | $$ |
| Emerald | 7.5–8 | Green | Oil / resin fracture filling | Caution — brittle, re-oil over time | $$$$ |
| Morganite | 7.5–8 | Peach to pink | Heat (stable) | Good | $$ |
| Garnet | 7–7.5 | Red, also green, orange | Usually none | Good (protect from knocks) | $$ |
| Amethyst | 7 | Purple | Heat (stable) | Good (avoid hard knocks) | $ |
| Opal | 5.5–6.5 | Play-of-colour, body white to black | Sometimes dyed / impregnated | Not recommended | $$–$$$ |
| Pearl | 2.5 | White, cream, black, pastel | Often dyed / bleached | Not recommended | $–$$$ |
Price tiers are relative: $ = budget-friendly, $$$$$ = rare and expensive. Fine alexandrite and untreated ruby sit at the top because good material is genuinely scarce.
Choosing a coloured stone for an engagement ring
If the ring will be worn daily and rarely taken off, start from hardness 8 and up, then sanity-check toughness. Sapphire is the workhorse — it comes in every colour including grey-blue teal and salmon-pink, it's a true 9 on Mohs, and heated sapphire is completely stable. Moissanite is harder still (9.25), brilliant, and the most budget-friendly hard stone we set. Ruby is sapphire's sibling (both are corundum) and equally tough; just steer clear of heavily glass-filled rubies, which are fragile and far cheaper than they look.
Alexandrite is a beautiful colour-change stone at 8.5, but natural material is rare and priced accordingly; lab-grown alexandrite is an honest, affordable alternative if disclosed. If you've fallen for emerald or opal, you can absolutely have it — just go in knowing it needs a protective setting (bezel or halo), gentle cleaning, and occasional maintenance. We'd rather set your dream stone with the right setting than talk you into a stone you don't love.
For the full picture on non-diamond centre stones, see our guide to engagement ring alternative stones, and if you're designing from scratch, the custom engagement ring guide walks through settings, metals and budget.
Stones we'd steer away from for everyday rings
Being honest here saves you a repair bill. Three of the twelve stones above are wonderful in earrings, pendants and occasional rings but a gamble in a daily engagement ring:
- Emerald — hard enough on paper, but brittle and almost always fracture-filled. The oil or resin dries out and the stone shows its internal fissures; ours come back to the bench for re-oiling every few years. Set it in a bezel, never clean it in an ultrasonic, and accept the upkeep.
- Opal — at 5.5–6.5 on Mohs with low toughness, opal scratches, chips, and can craze (fine cracks) from heat or drying out. Stunning, but not a knock-around stone.
- Pearl — at roughly 2.5 it's the softest thing in the case. Pearls scratch against almost everything and dislike perfume, hairspray and sweat. Keep them for necklaces and earrings.
None of this means "never." It means set it right and wear it kindly. Our on-site goldsmith builds protective settings for soft stones every week, and we'll tell you up front what a stone will and won't tolerate.
Frequently Asked Questions
What Mohs hardness do I need for an engagement ring?
For a ring worn every day, aim for Mohs 8 or higher so the stone resists scratching from everyday grit and dust. Sapphire and ruby (9), moissanite (9.25), alexandrite (8.5) and topaz (8) all clear that bar. Below 7.5, scratches accumulate quickly and the stone loses its polish over years of wear.
Is hardness the only thing that matters for durability?
No. Hardness resists scratches, but toughness resists chipping and cracking, and stability resists heat, light and chemicals. Emerald is reasonably hard yet brittle, so it chips despite its hardness. You want a stone that scores well on all three for daily wear.
Are gemstone treatments a bad sign?
Not at all — most coloured stones are treated, and many treatments are stable and permanent, like heating sapphire. The key is disclosure. Heated sapphire and ruby are fine. Oiled emerald and dyed stones are common but fragile, so you should know before you buy and get the treatment noted on your receipt.
Can I wear an emerald or opal ring every day?
You can, with care and the right setting. Both are vulnerable: emerald is brittle and fracture-filled, opal is soft and sensitive to knocks and temperature change. A protective bezel setting, gentle cleaning (no ultrasonic), and removing the ring for rough tasks make daily wear realistic. We set soft stones this way on our Coquitlam bench routinely.
Is moissanite as durable as sapphire?
Yes — slightly harder, in fact. Moissanite sits at 9.25 on the Mohs scale versus 9 for sapphire and ruby, so it resists scratches extremely well and is an excellent, budget-friendly choice for a daily ring. It's lab-grown, so it needs no treatment.
Which coloured stone gives the best value for daily wear?
Sapphire offers the best balance of hardness, toughness and colour range, while moissanite is the most affordable hard stone. Both hold up to daily wear with minimal fuss. Amethyst and garnet are budget-friendly at hardness 7–7.5 and fine with sensible care, just not as bombproof as corundum.