Before You Buy an Expensive Engagement Ring Stone
Most of the gems on this list have a Mohs hardness equal to or greater than 7. That’s a good indicator that a stone is suitable for the rigors of daily wear. Mohs hardness measures a material’s resistance to scratching. Household dust actually has a hardness of 7, equal to that of quartz, so most of these gems will easily resist scratches from this common hazard.
However, a high hardness, even diamond’s famous 10, doesn’t make a gem indestructible. Most gems, even diamonds, can shatter when struck. Tenacity is a measure of how well a material resists physical blows. All the gems on this list, except jadeite, have a “brittle” tenacity. (Jadeite has an unusually tough tenacity for a gem). Although protective settings are frequently associated with softer, more delicate gem materials like opals, you might consider such a setting for your engagement ring. Protective settings can also help keep your expensive engagement ring gemstone from snagging on clothing and possibly coming loose.
Many of the gems on this list are durable enough to be cleaned mechanically with a steam or ultrasonic system. However, some have inclusions or heat sensitivity and should only be cleaned at home with a soft brush, mild detergent, and warm water. Taking any of these gems to a professional jeweler for cleaning may be a wise choice.
Finally, if you’re having second thoughts… about the prices, take a look at these rare but inexpensive gem options.
“Emerald by day, ruby by night,” alexandrites change from green or blueish green under daylight to red or purplish red under incandescent light. Discovered in the 1830s in Russia, this unusual color change stone immediately became a favorite of the Czars. (Red and green reflected the Imperial military colors).
Alexandrites have a very high hardness (8.5), so they resist scratching very well, and make wonderful ring stones. However, in this case, rarity and demand make alexandrite one of the most expensive engagement ring gem options in the world. Even lab-created alexandrites are quite expensive.
You can learn more about buying alexandrites here.
2. Paraíba Tourmalines
Tourmalines come in every imaginable color and sometimes even show multiple zones of different colors. Most varieties are relatively inexpensive, but in 1989, the discovery of electric neon-blue to blue-green tourmalines in Paraíba, Brazil took the gem world by storm. Demand and prices for these rare paraíba tourmalines grew rapidly and continues unabated.
Since the initial discovery, tourmalines with similar colors have been found in Nigeria and Mozambique. Most major gemology labs describe these as paraíba tourmalines, too, since they all belong to the same tourmaline species, elbaite, and get their color from their copper content. Nevertheless, these gems are still rare, and those from Brazil sell at higher prices.
In addition to a hardness of 7-7.5, paraíba tourmalines have no cleavage. This means they are less likely to split, so they can better resist damage from blows.
You can learn more about buying paraíba tourmalines here.
3. Cat’s Eye Chrysoberyls
While many gemstones can show chatoyancy, a “cat’s eye” effect, cat’s eye chrysoberyls are the most valuable. However, not all chrysoberyls show cat’s eyes. In fact, alexandrites are a variety of chrysoberyl, and they very rarely display chatoyancy. Cat’s eye chrysoberyls usually have yellowish green, greenish yellow, or yellow body color. The most prized stones have a sharp “pupil” and demonstrate a neat “milk-and-honey” effect when held obliquely to a strong light — one side shows a “honey” body color, the other has a milky appearance.
Lapidaries usually cut cat’s eye chrysoberyls into cabochons to maximize the cat’s eye effect. With a hardness of 8.5, indistinct cleavage, and high luster, they make durable, luscious, glowing gemstones. Although traditionally used for men’s rings, they can be incorporated into any type of jewelry, including a delicately styled expensive engagement ring.
4. Colored Diamonds
Although white or colorless diamonds are the most popular and romanticized expensive engagement ring stones, they’re not rare. However, natural colored diamonds are incredibly rare, with only one occuring in 10,000 natural diamonds. If you want a truly jaw-dropping rarity with the fame, hardness, and dispersion or “fire” of diamonds, consider one of the following colored diamonds.
Natural pink diamonds are quite rare, yet most people have heard of them because of celebrities like Mariah Carey and Jennifer Lopez, who have received pink diamond engagement rings. The Argyle mine in Australia is known for producing pink diamonds. It takes 1 million carats of rough from the Argyle mine to yield a good quality 1-carat pink diamond!
Natural blue diamonds are also well-known but very rare. They tend to have light, grayish blue colors but are still quite stunning. Blue diamonds tend to cost tens of thousands per carat in lighter tones and hundreds of thousands per carat in darker tones. The deep grayish blue 45.52-ct Hope Diamond is one of the most famous gems in the world. Jennifer Lopez also received a blue diamond ring from an ex-husband.
Natural green diamonds can easily start at tens of thousands per carat. The 40.70-ct Dresden Green, the largest and most famous green diamond, is probably priceless due to its interesting provenance.
The rarest and most expensive of all diamonds, red diamonds cost at least hundreds of thousands per carat. The largest red diamond in the world, the internally flawless (IF), 5.11-ct Moussaieff Red, cost $1.32 million per carat. That also makes it the most expensive diamond in the world!
5. “Jedi” Spinels
First discovered in Myanmar in 2001, these neon hot pink spinels received the Star Wars-inspired nickname “Jedi” because they’re free of the “Dark Side.” This refers to their lack of dark tones, which can lower the value of spinels. The neon glow of “Jedi” spinels comes from their strong fluorescence. In other spinels, a high iron content inhibits this glow.
While most natural spinels are very durable and fairly rare, they’re also relatively unknown to many gem buyers. This usually keeps their prices down. “Jedi” spinels are very rare, but interest in them is growing. Eventually, this will drive up demand and prices. Be aware that vendors may try to market their spinels as “Jedi.” However, unless they exhibit that neon hot pink color, they don’t merit that designation.
“Jedi” spinels from the Man Sin mine (Mogok, Myanmar), on a broker’s hand in the Umbrella Market and on gem dealer Jeffery Bergman’s fingers. Photos by Jeffery Bergman, © 8th Dimension Gems. Used with permission.
You can learn more about buying spinels here.
The gem material known as jade can be one of two distinct minerals: jadeite or nephrite. Of the two, jadeite is much rarer and more expensive. Jadeite can occur in many colors, including white, orange, yellow, gray, black, and lavender. However, deep “Imperial” green is the most highly valued color of jade and only occurs in jadeite. When paired with translucence, such pieces are greatly prized. When polished to a high luster, jadeites will look amazing.
With a hardness range of 6.5 to 7, jadeite can have a hardness below that of household dust. This means some pieces may have an increased vulnerability to scratching. However, jadeite is also one of the toughest gem materials available. Jadeite has very high tenacity and no cleavage. This means it has great resistance to chipping and cracking.
Lapidaries will usually cut jadeites into cabochons for ring settings, but they can also make distinctive hololith rings, carved from a single piece of stone. Such an unusual ring with jadeite’s gemmy texture will surely catch the eye!
Jadeite’s toughness has inspired folkloric beliefs that it has protective properties, especially among the Chinese. Indeed, the “Jewel of Heaven” enjoys a strong consumer market in China and has even fetched the highest recorded price per carat of any gemstone. A green jadeite necklace sold for $9.3 million in auction at Christie’s in 1997.
You can learn more about buying jade — both jadeite and nephrite — here.
Rubellite is the trade name for purplish, orangey, or brownish red tourmalines that approach the color and saturation of rubies. Although rarer than rubies, rubellites are less costly. In fact, they’re the most affordable gemstone option on this list. Nevertheless, rubellite has had some notable devotees. In the 1880s, much of the rubellite mined in California was shipped to China to satisfy the Empress Dowager Cixi’s passion for this stone.
For an expensive engagement ring stone, rubellite can offer couples a variety of options. It comes in a wide range of beautiful reds: mauve, magenta, rose, pale pink, and blood red. Lapidaries can also cut these stones into beautiful faceted gems as well as cabs. Some cabs may even show a “cat’s eye” effect, due to tubular inclusions within the stone.
Although rubellites are durable gems, they often do contain inclusions. For this reason, don’t clean them with mechanical systems. Instead, use a soft brush, mild detergent, and warm water at home or else take them to a professional jeweler.
You can learn more about buying rubellites here.
8. Demantoid Garnets
Although many varieties of garnet are abundant and affordable, demantoids are extremely rare and very expensive engagement ring stone options. These gems come in green colors that rival emeralds but are far livelier. First discovered in Russia in the early 19th century, demantoids commanded the love and attention of the Czars and aristocracy. Carl Fabergé frequently used them in his creations. Not only do the finest demantoids have an intense green color, they also exceed the dispersion of diamonds and the brilliance (light return) of many gems, including rubies and sapphires.
While inclusions visible to the naked eye usually reduce the value of most gems, the yellow “horsetail” inclusions of radiating fibers shown by some demantoids can increase their value and add even more visual appeal.
Demantoids rarely occur in sizes larger than three carats. Because of their beauty and rarity, prices for demantoids can also rival those of emeralds. The hardness of demantoids can range from 6.5 to 7, so some stones may have increased susceptibility to scratching. Garnets may have some heat sensitivity, so clean demantoids only with warm water, detergent, and a soft brush
You can learn more about buying demantoids here.
9. Color Change/Blue Garnets
It was commonly thought that garnets existed in all colors except blue, until blue garnets were discovered in Madagascar in 1998. Incredibly rare gems, these color change garnets usually appear blue to greenish blue in sunlight and purplish pink in incandescent light. Their color change can be even more pronounced than that of alexandrite.
Because of their color change and rarity, blue garnets can fetch up to $1.5 million per carat! They’re now known to occur in the United States, Russia, and Turkey as well. The most expensive blue garnet was a 4.2-ct beauty that sold for $6.8 million in 2003.
The hardness of some garnets can range from 6.5 to 7.5, so some may have increased susceptibility to scratching. They may also have some heat sensitivity, so clean color change/blue garnets only with warm water, detergent, and a soft brush
10. Red Beryls
Related to aquamarines and emeralds, red beryls are the red variety of the beryl gem species. Gem-quality crystals occur only in the Wah Wah Mountains of Utah. Red beryl is so rare that it’s estimated there’s only one gem-quality red beryl crystal for every 150,000 gem-quality diamonds! Sizes over one carat are even rarer.
Red beryl can fetch up to $10,000 per carat. If you’re buying a red beryl, make sure it comes with a gem lab grade report and it’s not a simulated or imitation stone.
Due to inclusions, never clean this gem with a steam or ultrasonic system. Either use a soft brush, mild detergent, and warm water at home or take it to a professional jeweler.
A Bonus: 11. Natural Pearls
Although cultured, farm-raised pearls are readily available at affordable prices, natural pearls — formed in the wild — are exceedingly rare and can be incredibly expensive. To learn more about pearls, consult our pearl buying guide and our pearl engagement ring guide. Pearls also require significant extra care for cleaning, storing, and wearing, more so than any expensive engagement ring gem on this list.