Which Colored Gemstone Should You Choose?
A diamond is graded against a universal scale. A colored stone is chosen because of how it looks to you.
That difference is the whole thing. With colored stones there is no D-to-Z to hide behind — you are buying color, and color is judged by eye. Here is what actually separates them.
First: durability decides where you can wear it
Gemstone hardness is measured on the Mohs scale, 1 to 10.
| Stone | Mohs | Wear it as |
|---|---|---|
| Sapphire, ruby | 9 | Anything, including a daily ring |
| Topaz | 8 | Rings, with some care — can chip on a sharp knock |
| Emerald | 7.5–8 | Pendants and earrings; more fragile than the number suggests |
| Garnet, amethyst, citrine | 7–7.5 | Rings worn with awareness |
| Peridot, tourmaline | 6.5–7.5 | Earrings, pendants, occasional rings |
| Onyx | 6.5–7 | Beads and bracelets |
| Moonstone | 6–6.5 | Earrings and pendants only |
The stones, and what they are actually like
Sapphire
Blue is the classic, but sapphire occurs in nearly every color except red — pink sapphire in particular has become a favorite for engagement rings. What you are paying for is saturation: a vivid, evenly distributed blue costs far more than a pale or patchy one of the same size. Sapphire is hard, holds a polish, and is the most practical colored stone for daily wear.
Ruby
Chemically the same mineral as sapphire — corundum — colored red by chromium. That same chromium tends to produce internal fractures as the crystal grows, which is part of why untreated rubies of rich color are among the most expensive gems by carat. Ruby carries the same 9 hardness as sapphire.
Emerald
The color is unmatched and the trade-off is real: nearly every emerald contains inclusions, called the jardin. In emerald, visible inclusions are expected rather than a flaw, and they are part of how the stone is priced. Handle with more care than sapphire — avoid ultrasonic cleaners entirely.
Amethyst
Purple quartz, and one of the best values in colored stone. Large, clean, deeply saturated amethyst is affordable in a way sapphire never is. Good hardness for rings worn with reasonable care.
Garnet
Usually a deep, warm red — and consistently undervalued. A well-cut garnet with strong saturation reads richer than many rubies at a fraction of the price.
Blue topaz
Bright, clean, and available in large sizes for very little. London blue is the deepest tone; Swiss blue is brighter and more electric. Hard enough for rings.
Peridot
A distinctive yellow-green that occurs in no other common stone. Softer, so best in earrings and pendants.
Black onyx
Not a transparent gem but a dense black chalcedony, polished smooth, cut as a flat face, or faceted into beads. It provides contrast that no transparent stone can — which is why we set it with diamond and pair it with white pearl. Black onyx is a signature of the house.
Moonstone
Valued for adularescence — the blue-white glow that floats across the surface as it moves. Soft, so treat it gently. It is also one of the three June birthstones, alongside pearl and alexandrite.
What drives the price
For colored stones the order is different from diamonds. Color comes first — saturation and evenness account for most of the value. Clarity second, and with different expectations per stone (an emerald is judged against emeralds, not against sapphire). Cut third, which matters for how evenly the color reads. Carat last — size amplifies whatever the stone already is, good or bad.
This is why a 2 carat pale sapphire can cost less than a 1 carat vivid one.
Treatments — ask the question
Most colored stones on the market are treated. Heating sapphire and ruby to improve color is ancient, stable, permanent, and broadly accepted. Other treatments — fracture filling, dyeing, irradiation — vary in how well they hold up. None of this is a problem as long as it is disclosed. A seller who will not answer plainly is the problem.
A note on lab-created stones
Lab-created gems are chemically identical to mined ones and cost far less. We use created emerald in some designs and say so plainly on the product page. Whether that matters is a personal judgment, not a quality one — but you should always know which you are buying.
The same logic applies to diamonds, discussed in lab-grown vs. natural diamonds.
How we choose
We select colored stones at the source for color saturation and clarity, then set them in 14K and 18K gold at our New York atelier. Our gemstone pieces run from the hundreds into the low thousands — rings, earrings, bracelets, and pendants across every stone above.
Not sure which stone suits what you have in mind? Reach us at sales@isaacwestman.com or 1-347-389-0766.
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ISAAC WESTMAN® · New York · Founded 1982