Gemstone Hardness Scale- From Daily Durability to Proceed with Caution
By Stephanie Dore
You’re a little rough around the edges. And that’s ok. Maybe you trip over your own two feet, or drop your phone a lot, or forget your keys. Maybe you fall and skin your knee. Or drop things down the garbage disposal. It’s called life, and we highly recommend reveling in every minute of it. What we don’t want to do though, is ruin our most precious valuables in the process. Because, you know, money. And memories, of course. One of those valuables, to state the obvious, is your jewelry. And while diamonds are certainly hard, it might come as a shock to some that they are not, in fact, indestructible. Not to worry, there’s a little thing called the Mohs scale of mineral hardness (aka a gemstone hardness scale) to help you figure out just which gemstones will stand up to life and which ones might require you proceed with a bit more caution.
Testing how hard (or soft) the world around is isn’t anything new. I mean, we all do this as kids, right, trying to break or scratch things with other things. No? Just us? Well, that’s a different post. But on the subject — the earliest notation of scratching minerals against each other to compare their hardness was noted around 300 BC. But it wasn’t until 1822 when German geologist and mineralogist Friedrich Mohs created his namesake scale.
What it Is
So this scale, which is pretty much the standard as far as grading the hardness of gemstones in the jewelry industry, is based on the ability of one natural sample of mineral to scratch another mineral visibly. Yep, simple stuff really. On a scale of 1 (soft) to 10 (hard), does one rock scratch another rock? What the Mohs scale does not tell us, however, is a gemstone’s toughness. What’s the difference? Hardness is all about that surface stuff, scratchability. Toughness is more about inner strength, compressibility, elongation…can it stand up to impact versus surface scratches. This is important, but we’ll circle back.
The other thing to note about the Mohs scale is that it’s a 1–10 scale but the numbers do not fall at even intervals in terms of hardness. For example, the difference in hardness between a sapphire (9) and diamond (10) is much greater than a quartz (7) and a topaz (8).
We Love Surprises
But this isn’t one of them. So, diamonds are a 10 on the Mohs scale of hardness. They are the hardest natural material on Earth, and can, well, scratch anything. This hardness is one of the properties (besides its sparkle, duh) that makes diamonds so perfect for everyday wear, whereas a softer stone might get nicked by the little things we don’t really notice and eventually become dull, a diamond won’t. That little thing will stay nice and shiny for its whole life if properly taken care of. And yes, this includes lab grown diamonds (which are real diamonds)!
Here’s where it gets tricky. Diamond is hard, but it is definitely not tough. In fact, its rigid crystal structure means that if struck at a certain angle, perhaps a point, or along it’s thin girdle edge, a diamond is quite susceptible to breakage. Which is different from scratching. This is why shapes with points have prongs to protect them. It’s also why you shouldn’t wear your diamond jewelry, say, rock climbing. Diamonds can also scratch themselves, remember, which matters when you are wearing stacked rings with exposed diamond edges and when you store your jewelry for safekeeping. Just keep things separated and you’ll be all gravy.
A Second Sparkler
If you’re thinking about an alternative to diamond for your engagement ring and want to keep it sparkly and bright but still super durable, look no further than Moissanite. This stunner is actually a 9.25 on the Mohs scale, so you’re barely making a sacrifice. And TBH, it’s more sparkly than diamond. Yeah, yeah, we know. Not the same. See Moissanite has a different kind of sparkle, one that errs on the rainbow flash side of things instead of diamond’s bright black and white pattern of brilliance. But still. We love, love, love Moissanite for everyday wear and it’ll save you a pretty penny when it comes to getting more gemstone for your money.
Two of A Kind
The next step down from all that brilliance, is corundum at a 9 on the Mohs scale. Now, you probably know this crazy cool stone by the name of say, sapphire, perhaps? Well, guess what darling, it’s ruby too! That’s right, sapphire and ruby are actually the same stone! Yes, they’re both corundum, just different colors. We know, it’s nuts. The other cool thing? A 9 is still totally acceptable for day to day wear in any of your fave jewelry pieces. Sapphires and rubies are, of course, super popular, but also super durable.
While absolutely sumptuous, we don’t suggest taking a bite out of your favorite emerald. At a 7.5-8 on the Mohs scale, they’re still harder than your teeth! For reference, tooth enamel is about a 5! It’s about at the 7-8 level that you should start paying a bit more attention to how you’re wearing your gemstones, as the durability starts to get a little too soft for everyday, carefree wear. What do we mean? We mean, consider putting softer stones in jewelry pieces that don’t take as much wear, say pendants and earrings, whereas bracelets and especially rings take more of the brunt. But, yes, you can definitely still wear these stones in a ring if you’d like. Just make sure to take it off if you’re doing anything active and consider setting it lower profile, perhaps in a bezel…just something a bit more protective.
And Other Things
Topaz (8), aquamarine (7.5-8), spinel (8), and morganite (7.5-8) are all similar in terms of hardness, which gives you some seriously fun color options to choose from and still feel pretty okay about their everyday durability. From the palest blue to blushing peach to deep reds and browns and more, there’s a wide world of colorful gemstones out there.
But it’s as you get into this range of semi-precious gems that extra caution becomes important. Quartz, which includes both amethyst and citrine, is a 7 on the Mohs scale, as is tourmaline. You’ll often see these stones set in earrings and pendants instead of rings for exactly this durability concern. The same goes for tanzanite and peridot as well, which lean toward 6.5, and this is about as low as we suggest going for your “regular wear” jewelry.
The Softer Side
Here’s where it gets a little tricky. There are still plenty of beautiful gems that are lower on the scale than this. For instance, what about the stunningly iridescent opal, which is a 5.5-6.5 on the scale? Yes, you can for sure wear opal jewelry. You just have to be extra mindful about knocking it around, how you store it, and what substances you expose it to. The same goes for moonstone (6-6.5), turquoise (5-6), and most of all pearls, which are way down the scale at 2.5-4.5! Yes, you’ll see them all in jewelry, and we’re not saying no, we’re just saying: carefully. Think about how these stones are set, keep them away from other stones or hard surfaces that could scratch them, and protect them during both wear and storage from substances like lotions and perfumes as these can enter their more porous surfaces and damage their beauty.
We said we’d come back to it, so here we are. Now that you know everything about gemstone hardness, it’s time to talk about what else matters. Yep, you heard us correctly, hardness isn’t the only thing you need to worry about when it comes to gemstone durability for your daily life. That toughness thing comes into play, as does a gemstone’s internal structure, its inclusions, its treatments…you kind of need to know it all. Why? Well, toughness is great if you’re looking for a stone to carve, like jade or onyx, instead of a faceted, harder sapphire or diamond. The slightly softer surface makes carving easier, which is why you’ll see softer stones used for cameos or beads.
Inclusions come into play when they create a weak point in the gemstone’s structure. Heavily included stones might have inclusions that reach the surface or create more vulnerabilities, like a ding in the windshield that could eventually split if hit in just the right spot. This applies to things like emeralds, which are ok durability-wise, but also tend to have more inclusions. Or salt and pepper diamonds which are basically all inclusion. Treatments can also leave a stone more susceptible to breakage, so make sure you know exactly what you’re buying.
Is Your Mind Swimming?
Want to go for something colorful but we just totally freaked you out? Not to worry, we’ve got experts on hand to help you dive in. You can start with our little style quiz to design your own custom gemstone engagement ring or wedding set. Or reach out to our team at email@example.com (yes, that’s our direct line) and we’ll get you all sorted. No pressure, no commission, all color.