We have the ancient Greeks to thank for how we categorize gemstones. Diamonds, rubies, sapphires and emeralds they considered precious; every other one was merely “semiprecious.”
But are these classifications relevant today?
While it’s true the four precious gemstones are the most noticed at auction, there are times when certain high-quality semiprecious stones are actually rarer, and will realize a higher auction value.
In the end, it all depends on what “precious” really means to you.
There are literally hundreds of semiprecious gemstones ranging from the well-known opal, tiger eye, lapis lazuli and turquoise to ones that are not usually associated with fashionable jewelry such as musgravite, tanzanite, and alexandrite — with so many others in between. We’ll just focus on the gemstones most collectors are familiar with here, their birthstone, which will help provide a general idea as to the wide availability, value and collectibility of gemstones overall.
January – Garnet
The birthstone for the first month of the year is garnet, a silicate that is mostly red with many variations from light to dark. There are other colors, like green (rarest of all), yellow and orange. Expect a garnet to be valued at about $500 a carat, depending on its size, cut, clarity and color.
February – Amethyst
The birthstone for February, amethyst contains an iron oxide and other minerals like manganese that brilliantly project its wonderful dark-purple color. Mined mostly in Brazil and Uruguay, amethyst is a larger coarse-grain quartz easily bought for under $10 a carat.
March – Aquamarine
According to the Zodiac, March is Pisces (or fish), so it makes sense that the birthstone for the month is aquamarine, from the Latin for seawater. It is classified as a variation of a beryl with color mostly in the light greenish-blue hues. Aquamarine is mined primarily in Pakistan with an auction value of about $600 a carat or so.
April – Diamond
One of the four precious stones, diamond has its own category of desire both as jewelry and an adornment for thousands of years. Made from highly pressurized carbon in the deepest Earth, diamond is brought near the surface by underground volcanic activity over millions of years. One carat of cut and polished diamond can easily start at about $1,800 or so with variations up to $12,000 at auction.
May – Emerald
The second of the four precious stones, emerald is a member of the beryl family, like aquamarine, except with the addition of chromium that renders the color green. Most emeralds are mined from Colombia; a good-quality, one-carat emerald stone can start at about $550.
June – Pearl
This unusual gemstone isn’t as much a mineral as it is a living fossil. Made in nature from calcium carbonate secreted by a mollusk in saltwater (called nacre), a pearl is less a stone than it is a gem. Its natural hues range from stark white to black with many variations in between. A natural pearl can start at about $300 a carat.
July – Ruby
The third of the precious stones, ruby, can be confused with a garnet, especially when both have a similar deep-red color. To tell the difference, hold either up to the light — if there are two rainbows with no yellow or green bands, it’s a garnet. A one-carat ruby can start at about $350.
August – Peridot
Not as well known as other gemstones, the peridot nevertheless is classified as olivine, its shade of green similar to that of green olives. It’s not exactly mined as it is found within lava after volcanic activity, making them not as rare — except for the ones of gem quality that start at about $60 a carat.
September – Sapphire
The fourth of the four precious stones, sapphires, from the corundum family like ruby, are normally recognized as a deep blue, but they come in a variety of colors ranging from black to yellow, orange, green and even colorless (called fancy or parti-colored sapphires). A one-carat sapphire can start at about $450 and higher depending on quality and color.
October – Opal
What attracts so many to the opal is its iridescent colors that sparkle on a background of silky white, gray, green, blue and other colors with black being the rarest and most valuable (common opal is mostly just a white background and not as valuable). Patterns of color determine its value with a precious opal of white with fair iridescence having a value starting around $20 a carat with more color patterns having a much higher value.
November – Citrine
If you heat-treat an amethyst, the result will be a citrine, a yellowish gemstone in the quartz family, but it will show straight cracks under high resolution; a natural citrine will be cloudier. Citrines are available from as low as $10 a carat with a higher value for the more brilliant orange hue.
December – Blue Zircon
Another gemstone that isn’t particularly well known, the blue zircon is a nesosilicate that comes in a variety of primary colors, with the blue zircon being the most desired. Blue zircon will fade in direct sunlight, but its color returns when back indoors. Auction values will show blue zircon starting about $20 a carat.
Our list of gemstones is only a very small fraction of the hundreds of gemstones available in every color, brilliance, rarity, and radiance. Onyx, jade, agate, moonstone, obsidian, malachite, sunstone, and all manner of quartz also engender strong personal connections.
Just be careful. Many semiprecious stones can be confused with other gems, and there are artificial gems, as well, but they “completely different physically, chemically and optically” from the natural gems they copy, says Jewelrywise.com. In spite of those inherent differences, some lab-generated gems may be very similar to authentic natural examples. Don’t be afraid to ask a jeweler about a gem’s background before making a purchase.
Hardness of semiprecious stones matters, too, especially when designing personal jewelry. The Mohs scale classifies each stone, precious or semiprecious, as to its ability to withstand constant use with 1 being the softest (talc) and 10 the hardest (diamond). You don’t want a soft stone, such as amber, to be used on a ring that is worn daily.
With so many semiprecious stones to choose from, it’s no wonder that they are so affordable overall, with most selling within the $20 to $50 a carat range. It all depends on size, color, hue, rarity and setting. Of course, the rarest and most valuable gemstones, such as alexandrite, at $70,000 a carat; or musgravite, at about half that; are just as collectible as diamonds.
“You might assume high-end gems and jewelry make good investments, but that’s not necessarily the case. Gems of lesser value often appreciate more and are easier to liquidate. Many well-informed investors choose low to moderately priced gems,” according to the International Gem Society’s article “Making Money Investing in Gems: 5 Top Rules.”
Simply stated, if you buy semiprecious stones with an eye toward later resale, you should always make your purchases from trusted sellers and consider decorative settings later on if your goal is to increase the value of your investment. The first rule of collecting, however, is that you should always buy what you like first. Unless you buy for resale, the investment aspect should be a secondary consideration.
There’s a lot to learn about semiprecious stones, and the Gemological Institute of America and International Gemological Institute are among the trade groups that can help you to become an educated buyer. Just know that there is a gemstone — precious or otherwise — that the natural world created just for you. When you find it, you will feel a connection to nature.