You’ve probably heard the term “a diamond is forever”. But did you know this romanticised saying was originally a tagline for an advertisement?
It comes from the diamond company De Beers, which launched its “A Diamond is Forever” campaign in the late 1940s. The campaign was a huge success and forever changed the way we think not just about diamonds, but about engagement rings.
Today, the diamond is the de facto precious stone for proposal rings around the world. De Beers has managed to sell us all the idea that you a diamond ring is essential to prove your love.
But here’s a second fun fact: The traditional engagement ring was not a diamond—it was a blue sapphire. In the mediaeval era, sapphires were a symbol of love, commitment, and fidelity; it was believed that a sapphire would change colour or fade if the wearer was unfaithful or dishonest.
Sapphires aren’t the only coloured gemstone with rich history and symbolism. For example, have you ever thought about how rubies are the colour of our most intense emotions like love, passion, and rage? Then we have emeralds, green jewels linked to the lushest landscapes and deepest greens—Ireland is famously known as the Emerald Isle, and Seattle, in Washington state, is called the Emerald City.
Diamonds are forever, but coloured gemstones are just as timeless. In this article, we’ll share expert insight from Alex, a gemstone collector and owner of the Ministry of Gemstones, on how to select a high-quality coloured gemstone for your proposal ring that is beautiful, meaningful, and enduring as an investment for generations to come.
Guide to Choosing an Investment Grade Gemstone for Your Proposal Ring
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- The best investment-grade gemstones for your proposal ring: the Four Kings of Gemstones
- Introducing the 4Cs—cut, clarity, colour, and carat
- 4Cs: Which is the most important C for coloured gemstones?
- What clarity is best for coloured gemstones?
- 4Cs: Which is the most important C for diamonds?
- What clarity of diamond is best?
- Which diamond is the best to invest in?
- Why Carat matters for investment-grade gemstones to hold their value
- Are lab-grown gemstones good for investment?
- How to choose a lasting gemstone for a proposal ring
1. The best investment-grade gemstones for your proposal ring: the Four Kings of Gemstones
When investing in coloured gemstones, the first question you’ll probably ask is what type of coloured gemstones to invest in. The answer? Diamonds, rubies, sapphires, and emeralds, otherwise known as the Four Kings or the Four Precious Stones. Traditionally speaking, these are the only gemstones in the world that are considered truly precious.
But as far as proposal rings are concerned, Alex recommends 1 coloured gemstone above all others.
“If someone says they want an engagement ring, the first thing I would recommend is a sapphire,” Alex tells me. “Sapphires come in different colours—yellow, green, blue, pink, and so on. You’re sure to find a colour that speaks to you.”
Sapphires pretty much come in every colour—even “white”, or “colourless” like a diamond—so you’re bound to find a colour you love. My personal favourite is the padparadscha sapphire, which comes from the Sinhalese word for “lotus blossom”. Like the lotus flower, padparadschas are a unique blend of orangey pink. They can capture the sweet youthfulness of a baby pink blush while also exuding a refined elegance through its orange undertones.
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2. Introducing the 4Cs—cut, clarity, colour, and carat
There are the Four Kings, then there are the 4Cs—cut, clarity, colour, and carat. These are the 4 main factors that determine the quality and value of a diamond. Here’s a quick recap before we go into which to prioritise for an investment grade gemstone:
- Cut: The cut of a diamond determines how well it reflects light, giving it brilliance and sparkle.
- Clarity: Clarity assesses the diamond’s internal and external imperfections, with higher clarity diamonds appearing clearer and more flawless.
- Colour: Colour measures the diamond’s hue, with colourless stones being the most sought-after for their purity and value.
- Carat: Carat refers to the diamond’s weight, with larger carat sizes generally being more valuable.
3. 4Cs: Which is the most important C for coloured gemstones?
“With coloured gemstones, the most important thing is colour,” Alex explains. Colour is the most important thing because, well, that’s the whole point of coloured gemstones isn’t it? Colour. A rare colour could make any gemstone, even one with relatively poor clarity or lower carat weight, very valuable.
For example, a rich royal blue (not just any blue!) and the orangey-pink padparadscha are among the most rare and valuable sapphire colours. Looking at the 1.5-carat gemstones currently at the Ministry of Gemstones, a yellow sapphire costs $1,650 and a white sapphire $1,000. But a padparadscha of the same carat weight? $3,500. As for royal blue sapphires, that’s the colour that takes the crown for the most expensive gemstone in Alex’s possession—$80,000 for a 5.5-carat piece.
4. What clarity is best for coloured gemstones?
While the diamond clarity scale isn’t usually used with coloured gemstones, the same “flawless to the naked eye” principle that Alex talked about can be applied.
“In terms of clarity, generally it’s good as long as it’s eye-clean,” Alex says. Eye-clean gemstones are gemstones whose blemishes and flaws (called inclusions) are not visible to the naked eye.
In rare cases, some gemstones can even be worth more when inclusions are present. For example, demantoids are rare, brilliant green garnets that can cost as much as $10,000 per carat. What makes some pieces so valuable? Their “horsetail” inclusions—fine, golden fibres that resemble a horse’s tail. These inclusions make the gem more rare, mark its natural origin, and are deeply mesmerising to look at:
5. 4Cs: Which is the most important C for diamonds?
While all 4 factors affect the value of a diamond, the cut is often thought to be the most important of the 4Cs. Cut affects how well its facets interact with light, making it sparkle and appear more vibrant, even if the diamond is flawed in other aspects. With an ideal cut, the diamond will refract light at the perfect angles to direct light back to the top of the stone (and into your eye). Here are some illustrations to show you what that means:
6. What clarity of diamond is best?
Diamonds are graded on their clarity from FL (flawless) to I1-3 (included). FL means the diamond is perfect—there are no flaws in it, even if you were to look at it under magnification. On the other end of the spectrum, I1 – 3 diamonds will have visible inclusions, such as a tiny mineral fragment or fracture, that affect the diamond’s clarity and appearance.
For the perfect proposal ring diamond, shouldn’t we aim for FL or IF then? Short answer: No.
“From VS (very slightly included) onwards to FL, you can’t see the diamond’s flaws with your naked eye. You’d have to use a loupe to zoom in 10 times to see them, and we won’t be carrying around a loupe in daily life!” Alex laughs. A loupe is a handheld magnification tool used to see small details more clearly.
“Diamond prices jump like crazy from VS to VVS and to IF. So—and this is just my opinion—I can’t justify the price difference when a VS diamond looks just as nice as an IF one,” Alex shares.
I completely agree with him. Paying a few extra hundreds or even thousands of dollars for fewer inclusions that you can’t see anyway doesn’t make sense to me. I would personally go for VS1 or VS2 if I had to choose a white diamond. But if I had free rein, I would choose a more colourful option.
7. Which diamond is the best to invest in?
“If you’re looking at diamonds, go for coloured diamonds as opposed to white diamonds,” Alex advises. “The pinks, blues, greens, greys, and so on. These are extremely rare and tend to appreciate more.”
A word of warning: coloured diamonds are very expensive. For example, pink diamonds can cost up to $700,000 per carat. Argyle pink diamonds, mined from Australia’s Argyle Diamond Mine that closed in 2020, range from US$500,000 (S$676,500) to over US$1 million per carat depending on how saturated they are in colour. The mine only produced about 60 pink diamonds each year, and now that it’s shut down, the rare pink diamonds that came out of that mine are a finite supply.
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There is also a small group of ultra rare diamonds called Type 2a diamonds, thought to be the purest and rarest diamonds in the world. To the naked eye, these may not look very different from your regular diamond. However, compositionally, these gems are prized for their lack of nitrogen impurities, granting them exceptional transparency and brilliance. These pure carbons treasures are so rare that they represent only 1-2% of the world’s diamonds.
“Type 2a diamonds are extremely rare and can cost $34,000 or higher per carat,” Alex tells me. “A 2 carat specimen can be over $100,000. If you’re looking for investment grade gemstones, these will hold their value better than a typical white diamond.”
8. Why Carat matters for investment-grade gemstones to hold their value
People often think “how many carats?” is synonymous with “how big is that gemstone?”, but carat is not about size. Carat refers to the weight of a gemstone. While it can give you an idea of how big a gem is (e.g. a 1 carat piece will never look bigger than a 5 carat one), a gemstone’s visual size depends a lot on how it’s cut. For example, a shallow cut would yield a larger gem face, while a gemstone of the same carat weight but a deeper cut might yield a smaller gem face.
“If you want something investment grade, you need to look at gemstones that are 3 to 5 carats,” Alex tells me
Why? Turns out, it’s about rarity.
“If you go to gemstone or jewellery shops, you can quite easily find 2 carat pieces. But if you want something to invest in, look for something not easy to find—then it can command a certain price,” he explains.
Alex warns that—like all investments—this isn’t a guarantee. Acquiring a shiny 3-carat rock today doesn’t mean a 100% return on your investment is promised to you 5 years later.
What will help you is choosing a 3 to 5 carat gemstone that is 1 of the big 4: diamonds (coloured ones!), rubies, sapphires and emeralds. When you own a large specimen of one of the Four Kings, prices jump.
“Take a 2 carat and 6 carat ruby, for example,” Alex says. “A 2 carat one can be $20,000 to $40,000. But a 6 carat one can reach $15 million because it’s that difficult to find a ruby of such a size.”
For a real life example, this 0.89 carat royal blue sapphire of Alex’s costs $1,500.
At the same time, this huge, stunning 5.5 carat royal blue sapphire costs $80,000—the most expensive gemstone Alex currently has at the Ministry of Gemstones. Its colour is alluring, and its size almost unbelievable.
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Yes, large gemstones are going to cost a lot more. But as far as investment goes, these are the pieces that are rare and that are more likely to continue commanding high (or higher and higher) prices years down the road.
9. Are lab-grown gemstones good for investment?
While lab-grown gemstones are just as beautiful as natural ones, they’re not as good an option for long-term investment because they aren’t rare.
“The keyword is ‘finite’,” Alex tells me. “Natural gemstones are a finite resource. They can’t be mass produced, so the supply is more limited.”
While natural gemstones were formed over millions of years through natural geological processes, their lab-grown counterparts can be produced in controlled environments in a matter of weeks or months. Because their supply is essentially unlimited, they lack the scarcity that underpins investment value. In fact, technology gets better every day, and creating lab-grown gemstones can only get easier and easier.
Think about it: you might see a 5 carat natural pink diamond in a museum, but would anyone display a lab-grown diamond, even if it was 10 carats? One is a geological marvel built over millions of years, while the other is simply a successful laboratory procedure.
That said, lab-grown gemstones have a lot going for them. They’re generally more affordable, ethical, and of good quality since they are cultivated under controlled conditions. If you’re just shopping for a gemstone that looks the part and fits your budget, they’re a fantastic choice. Just don’t mistake your purchase for a long-term investment.
10. How to choose a lasting gemstone for a proposal ring
Investment grade or not, you want the gemstone on your proposal ring to last as a symbol of your long-lasting commitment to each other. So let’s put investment value aside for the moment and talk about perhaps the most essential thing to be aware of: not how much the gemstone is worth, not how rare its colour is, but simply how easily it can scratch or break.
Introducing the Mohs scale. This scale is used to describe a material’s hardness—how easy it is to scratch. Diamonds top the scale at 10, glass is 5.5 to 6, and talc found in baby powder and makeup comes in at 1.
The Mohs scale is simple to understand; a material that’s got a higher number on the scale can scratch a material with a lower number. For example, did you know that household dust can scratch glass? Dust contains tiny bits of quartz, a mineral that registers as 7 to 7.5 on the Mohs scale.
That means any gemstone with a Mohs scale number lower than 7 can be scratched by dust. For this reason, Alex doesn’t recommend apatite and sphene to be used as gemstones in a ring—these are between 5 to 5.5 on the Mohs scale. “These are more suitable as a pendant than a ring, but wear at your own risk,” Alex says.
I hope this guide helped you on your journey to find the perfect gemstone for your proposal ring. If you want to know more about Alex’s collection, check out my first interview piece with him.
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About the author
Vanessa Nah pens articles on the ins and outs of buying your first home, the T&Cs of credit cards, and the ups and downs of alternative investments. A researcher at heart, she gets a kick out of breaking down complex finance concepts for the everyday Singaporean. When Vanessa’s not debunking finance myths, you’ll find her attending dance classes, fingerpicking a guitar, or (most impawtently) fulfilling her life mission to make her one-eyed cat the most spoiled and loved kitty in the world.
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