Gem Buying Guide
How to Buy a Gemstone
The good news is we can teach you about gemstone quality. After you read our gem buying advice, you will know more than the average jeweler. The bad news is that you will have to read ALL our gemstone buying advice: gemstones are much more complicated than diamonds (which is why most jewelers don’t know much about them). So concentrate!
Diamonds have accepted grades for color and clarity and so it is possible for a price list like the Rapaport Diamond Report to exist. Gemstones have no grading system, each variety has individual value factors, and within each gem variety, quality dramatically affects price: a ruby can be worth $10 or $1,000,000.
Everybody agrees what the best stone is, that’s easy. But the best buy? That’s tricky. Hold on, we’ll get there!
First, the basics. Like diamonds, gemstone quality and value are evaluated according to the "four Cs": color, clarity, cut, and carat weight. For ruby, sapphire, and to a lesser extent emerald, country or origin also affects value. Unfortunately, colored gemstones are also commonly treated, so that also affects value for ruby, sapphire and emerald in particular.
Let’s start with the most important gemstone value factors, color, clarity, and carat weight.
Gem Buying Guide
Color is the key factor. But don’t assume that the darker the color, the better the stone. That isn’t true: color can be too dark, like some sapphires that look more black than blue. Think grass green, not forest green. Fire engine red, not burgundy. The more bright and vivid the color, the better.
In precise grading terms: clear, medium-tone, intense and saturated primary colors are the most preferred. Pure blue, not greenish blue. Pure red, not purplish red. Muted colors and colors between hues, which you might find very attractive, are usually less expensive. Look at the color in different kinds of light.
The next most important factor affecting value is clarity: clear transparent gemstones with no visible flaws are the most valued. There is no standardized grading system for clarity: it varies by gem variety. With colored gemstones, if the inclusion doesn’t show in the face up position, it generally doesn’t matter at all. (unlike diamonds which are graded upside-down at 10x magnification). Some varieties, notably emerald and red tourmaline, are very rare without inclusions of some kind so the price structure takes this into account. Pastel colored gemstones show inclusions more, so they generally detract more from the value for pale stones.
In rare cases, inclusions can increase value. Special effects like the star in star sapphire and the eye in cat’s-eye chrysoberyl are caused by inclusions. Inclusions can also be a birthmark, proving that a gemstone is from a particular place. So "horse-tail" inclusions in demantoid garnet make it more valuable because they prove it came from Russia. But more about origin later.
Carat Weight and Prices
Gemstones are sold by weight, not by size. Prices are calculated per carat, which is one-fifth of a gram. Some gems are denser than others so the same weight stone may be a different size! For example a one-carat emerald is a bigger than a one-carat ruby. Just like diamonds, the carat weight also affects the price: large gemstones are more rare, so the price per carat is higher. But practically, this doesn’t make much of a difference with common gems like amethyst, citrine and blue topaz. It really kicks in for ruby, emerald, sapphire, alexandrite, tsavorite and demantoid garnet, Paraiba and rubellite tourmaline, spinel, and pink topaz.
Another important quality factor, which makes a big difference in a gem’s beauty, but may not add much to the price is cut…
Gem Buying Guide
A good cut is something that may not cost more but can add or subtract a lot of beauty. A well-cut faceted gemstone reflects light back evenly across its surface area when held face up. If the stone is too deep and narrow, areas will be dark. If it is too shallow and wide, parts of the stone will be washed out and lifeless. The best way to judge cut is to look at similar gemstones next to each other.
Gem Buying Guide
Consider the Gem Alternatives
We recommend buying the best quality gemstone you can afford. In general, smaller gemstones of higher quality appreciate more over time than larger stones of lower quality. If your budget is too small to buy the quality you want, consider buying a higher quality gemstone from an unusual variety. Mediocre rubies, emeralds and sapphires cost a lot more than fine garnets, tourmalines, tanzanites, and other exotics.
In general, gemstone pricing within each variety follows common sense: the more beautiful the gemstone, with the final visual effect of all the quality factors, the more valuable it is. Don’t be afraid to choose what looks best to you!
Different varieties have different price ranges. some varieties are lower in price because they are readily available, some because the color isn’t very popular (brown and yellow stones, for example), some because the material is relatively soft, some because they are too rare to create demand and some because no one has heard of them or they have a weird name. You think I am kidding? Why does tanzanite cost more than tsavorite or spinel? A pretty name is the only explanation.
Here is a thumbnail guide to prices of different gem varieties, assuming good, but not great, quality:
- BIG THREE: ruby emerald and sapphire
Expect to pay between $250 and $10,000 per carat. Emerald and ruby cost more than sapphire, particularly in large sizes.
- NEW CLASSICS: tanzanite, tourmaline, aquamarine, imperial topaz, and tsavorite garnet
These gemstones are sometimes available in standardized sizes but fine stones are one of a kind and jewelry will have to be made specifically for the stone. Prices range between $50 to $1,000 per carat, with tsavorite easily reaching $3,000 per carat.
- CONNOISSEUR GEMS: black opal, jadeite, pink topaz, chrysoberyl cat’s-eye, fancy colored sapphires, demantoid garnet and alexandrite.
These gems are sought after and prices range from $250 to $5,000 per carat, although alexandrite with a good color change will command at least $10,000 even in a one-carat size.
- COLLECTOR STONES: spinel, zircon, moonstone, morganite and other beryls, and many rare gemstones.
Collector’s gems are not available in quantity to be marketed effectively so you get a lot of beauty for the money. Red and hot pink spinels can command a few thousand per carat but most of the gems in this category will sell for hundreds not thousands.
- AFFORDABLE GEMS: amethyst, white opal, citrine, ametrine, peridot, rhodolite garnet, blue topaz, iolite, chrome diopside, kunzite, andalusite, and ornamental gemstones such as lapis lazuli, turquoise, onyx, chrysoprase, nephrite jade, and amber.
These gems combine great color with reasonable prices and good availability: prices for these gemstone range between $5 and $100 per carat.
Gem Buying Guide
Most gemstones are treated. If you want one, you basically have to just get over it. Or buy a garnet, peridot, iolite, spinel, chrysoberyl, or alexandrite, which are basically the only gemstones that aren’t doctored.
That being said, the trade distinguishes between good treatments and bad treatments and so should you. Why? Good treatments are the basic ones that everyone expects to have happened unless you can prove otherwise. Everyone in the business basically ignores these when calculating prices. Bad treatments affect value and these gems are "special" products that not everyone will carry or buy. They may not hold value as well as normal products. They are, in a sense, taboo.
Trade accepted treatments:
- heating ruby and sapphire
- putting organic resins and wax in emerald
- heating amethyst, aquamarine, citrine, tanzanite, tourmaline, precious topaz, and zircon
- irradiating blue topaz (it is all irradiated: if you want it, accept it)
- waxing jadeite, lapis lazuli, and other ornamental gemstones
- dying onyx black (it isn’t)
- bleaching pearls white
- glass filling of ruby
- diffusion treatment of sapphire
- epoxy resin in emerald (the trade is currently fighting about this one: it’s more permanent so in a sense may be better but it offends traditionalists and who knows what these things will look like in 20 years.)
- dyeing opal black, lapis blue, or any other dye treatment
- epoxy treatment of jadeite (known as B-Jade in Hong Kong)
Trade-accepted treatment comes into play as a value factor at the very top of the market: fine ruby, sapphire, and emerald that is certified to be untreated will command a premium. Another value factor that mainly affects the gems in the top 1% of the market is country of origin, which we discuss next...
Gem Buying Guide
Country of origin matters in the prices of high-end ruby and sapphire but it doesn’t have to matter to you. If a major lab says that a ruby is from Burma or a sapphire is from Kashmir or Burma, it costs more than an identical stone without confirmed origin. Are you buying a gem that is important, say $20,000 or up, with a certificate? Then you need to think about origin. If not, don’t worry about it other than the fact that it is kind of cool to know where a gem is from.
A few things you need to know about origin if you are thinking of paying for one of these premium gemstones:
- GIA doesn’t grade origin. The major labs that do so, in order of preference, are: 1) Gubelin in Switzerland, 2) SSEF in Switzerland, 3) AGTA in New York, 4) American Gemological Laboratories in New York.
- Origin is guesswork. Only some stones show evidence and the limits of non-destructive testing means almost no certainty. And geology doesn’t respect national boundaries. The ruby deposit in Vietnam is geologically almost identical to Burma’s deposit.
- Origin became important because it was a shorthand for color. If you can get the same color from a different mine, what’s the difference?
- Ruby from Burma, to a connoisseur, means ruby from Mogok, not Mong Hsu. If you are going to pay a premium, make sure you are getting the real thing.
- For emerald, the color of Colombian emerald and African emerald are different. You can almost never confuse the two, so the question of country of origin really just means color.
I hope you enjoyed the Guide, Make the Right Choice.