Diamonds are central to the work I’m writing, so I’ve had to give myself a crash course on them: their natural history, their human history, how they are mined, how they are shaped and polished, how they are sold and how they are treasured. It’s a fascinating story because diamonds are a substance that everyone understands as precious and valuable, but at the same time, people generally have no idea how to understand their worth.

I’ll try to untangle some of this mystery and put diamonds in the historical context of the Dutch Golden Age, and along the way, I hope to give some helpful hints about how the average person can better shop for diamonds without feeling they are being horribly taken advantage of. After all, I’m not selling anything (other than hopefully a novel someday soon), so I have nothing to gain.

So, from the very beginning.

What is a diamond, anyway? Chemically speaking, a pure diamond would be made of the element carbon alone, the same as graphite. But obviously, there’s a world of difference between the two. Few people would cherish a pencil lead on their ring finger, and only a fool would throw a diamond ring into a fireplace.

What’s the difference, then? Two things: Heat and pressure. Diamonds are formed when carbon trapped far beneath the earth’s surface — ninety miles or more beneath our feet — is subjected to temperatures of at least 2,000ºF (1,050ºC), which puts the carbon under extreme pressure. This environment doesn’t occur everywhere on earth. It’s thought to be found mainly the the stable areas of the earth where there are no borders of tectonic plates nearby. After formation, volcanic activity subsequently moves the diamonds toward the surface.

Carbon happens to be one of the most common elements around, but diamonds are exceedingly rare. That’s because the conditions needed to form them are so extreme, and the distance they must travel toward the earth surface so vast. They cannot be found just anywhere on the earth’s surface, but only in a few places. In modern days, diamonds are found in 35 countries, but the top five producers are Russia, Botswana, Canada, Angola and South Africa.

Even so, diamonds are not the rarest gemstone around. Rubies, emeralds and sapphires are rarer, and as a result, cost more on a per-carat (weight) basis.

So what makes diamonds so special, then? Certainly there are other gemstones around. I’m particularly fond of emeralds, in case you’re wondering. Rubies have been cherished since biblical times (Proverbs 31:10-31: “How precious is a woman of valor / her worth is beyond rubies …”). Sapphires were revered back to ancient Persian times. Yet among them all, diamonds have been revered as the supreme gemstone.

One thing that makes diamonds unique is their hardness. Geologically speaking, “hardness” means a mineral will not scratch. In fact, they are the hardest mineral out there. It’s where they get their name from: the Greek word adamas, meaning indestructible or unbreakable. Geologically, it rates a full 10 on the Mohs Scale that rates hardness; it chemically identical twin graphite, by comparison, is rated a 1 to 2. 

Other gemstones don’t compare. Rubies and sapphires rate a 9. Emeralds, a mere 7.5 (the same as hardened steel). Jade, a 6-7. What this means is that diamonds won’t scuff or ding up easily, no matter how they are used. They don’t “age” with use. They will remain unscratched, which means they will sparkle as much the day they are first polished as they will 100 years later, if you keep it clean.

Paradoxically, diamonds are at the same time very brittle. That means that they can relatively effortlessly be cut and chipped into different pieces. And it doesn’t take another diamond to do this. It can be done with a steel hammer.

Yet these things can also be said of sapphires, rubies and emeralds, So this alone doesn’t explain why diamonds are valued so much more. What’s going on?

It comes down to one simple thing: demand. People simply want diamonds — they always have. Royalty have prized diamonds back to ancient times. When Archduke Maximilian of Austria proposed to Mary of Burgundy with a diamond engagement ring, he kicked off a fad that has yet to become passe. Ever since the middle class rose and people began to have extra pocket change, people other than royalty have dreamed of having a diamond of their own — or giving one to someone they love.

It’s demand that drives the value of these stones. Case in point? The “chocolate diamonds” you may have seen at some jewelry stores. Did you know that these brown diamonds used to be considered junk diamonds because they were off color? But rebrand them as “chocolate” and put a multi-million dollar marketing campaign behind it, and all of a sudden you have people willing to throw their wallets at them.

And don’t think I’m judging, because I was in love with those things myself until I realized they were using marketing as a way to jack up the price on off-color diamonds that otherwise would be worth much less. 

In fact, marketing has driven a lot of the value of diamonds over the last two centuries especially. It’s almost unthinkable to propose marriage without a diamond (how do you know if they’re serious without that???) and slogans like “a diamond is a girl’s best friend,” or “diamonds are forever” are ubiquitous.

But even knowing all this, I still value diamonds. I’ve bought a few myself, usually just small things, but I sweated out the purchase of an engagement ring. That was a months-long process that included the selection of one particular stone cut one particular way, and I can share how I picked it and why. But that’s a story for another time.