Random Gemstone Generator

What the gemstone generator does

You want a stone. Maybe for a character, maybe for a name, maybe for a game, maybe you are down a rabbit hole at one in the morning and you want to know what a poudretteite is.

This gives you one. Pull a batch and about half of them will be stones you have never heard of, which is the good part.

What follows is why that is. There is no agreed definition of the word gemstone, the hardness scale you learned at school is not measuring what you think it is measuring, and two of the most famous stones on earth are the same mineral wearing different jewellery.

How to use it

1. Choose how many you want. Pull a handful if you are browsing, one if you want a subject.
2. Press Generate. A fresh set every time.
3. Press Copy to take the set with you.

Nobody can tell you what a gemstone is

Try to define it. Go on.

A mineral? Then pearl is out, and amber, and jet, and coral, and ivory. Those are all animal or plant. None of them is a mineral and every jeweller on earth sells them.

Something rare? Then quartz is out, and quartz gives you amethyst, citrine, agate, carnelian, onyx, jasper and tiger's eye. Quartz is one of the most common substances in the crust of the planet.

Something hard? Then pearl is out again, and so is amber, and so is malachite, which you can scratch with a coin.

Something beautiful? Now you are not defining a thing. You are describing a decision.

And that is the honest answer. Gemstone is not a category that exists in the ground. It is a category that exists in a shop. A gemstone is a piece of the earth that somebody decided was worth cutting, and the moment enough people agreed, it became one.

Which is why a list of them is such a strange thing to read. Salt is a mineral with a crystal structure and a hardness and a name, halite, and under the right conditions it grows into perfect glassy cubes. Nobody puts it in a ring, because it dissolves. But it is not disqualified by nature. It is disqualified by a shower.

The scale everybody knows, and what it hides

You learned this one at school. Talc is 1, diamond is 10, and everything else sits somewhere in between.

Friedrich Mohs came up with it in 1812, and the reason it survived two hundred years is that it is brilliantly practical. It does not need a laboratory. It needs two rocks. Whichever one scratches the other is harder. That is the whole method, and a geologist can run it in a field with a pocket knife.

Here is what nobody mentions afterwards. Those numbers are not quantities. They are places in a queue.

In 2006 a team at Minnesota went and measured the first nine Mohs minerals properly, using indentation instead of scratching, and tested hardness, fracture toughness and elastic modulus. Their conclusion was blunt. None of the properties they measured increases consistently or linearly with the Mohs number across the scale.

So the gaps are a lie of presentation. Corundum sits at 9 and diamond at 10, one step apart on the poster, tidy as anything. In terms of what it actually takes to scratch them, that single step is a cliff. It is by far the biggest jump on the scale, and the scale does not tell you, because the scale was never built to tell you. It was built to rank, and we have been reading it as a ruler ever since.

There is a second thing hiding in there too. Scratching is not just hardness. When you drag one mineral across another you are loading it and shearing it at the same time, so what you are really testing is a mixture of hardness, toughness and how the thing likes to break. Which is why a diamond is the hardest natural substance on earth and you can still split one with a well aimed tap. Hard is not the same as tough. Hard means it resists being scratched. Tough means it resists being shattered. Jade is nowhere near diamond on the Mohs scale and it is far harder to break, which is exactly why people have been carving tools out of it for six thousand years.

Ruby and sapphire are the same rock

This is the one that gets people.

Ruby is corundum. Sapphire is corundum. Same mineral, same formula, aluminium and oxygen, both a 9 on the scale.

The difference is contamination.

Slip a trace of chromium into the crystal while it grows and it comes out red, and we call that a ruby. Slip in a bit of iron and titanium instead and it comes out blue, and we call that a sapphire. Same rock. A rounding error of impurity, arriving at the wrong moment a few hundred million years ago, and one of them is the most valuable red stone on earth while the other one is a completely different word.

It gets funnier. Sapphire is not even blue by definition. Corundum comes out pink, yellow, green, orange, colourless. All of those are sapphires. The trade calls them fancy sapphires and prices them accordingly. But pink corundum is a problem, because at some point along the gradient from pink to red somebody has to decide whether it is a pink sapphire or a ruby, and there is real money resting on which side of that line it lands.

There is no line in the rock. There is a line in the industry, and it moves depending on who you ask and which country you are standing in.

Pull corundum, ruby and sapphire out of this generator and you have pulled the same mineral three times. The stone did not change. Only the name did, and the name is where the money is.

Where these come from

The stones here come from a list our team put together and checked by hand. Press the button and one is drawn out of it at random.

That is the whole mechanism, and it runs on your own device.

How amethyst stopped being precious

There is a split you have heard your whole life. Precious stones and semi precious stones. Diamond, ruby, sapphire and emerald on one side. Everything else on the other.

It sounds ancient. It is Victorian, and it is marketing.

Amethyst is the proof. For most of recorded history amethyst was in the top tier. It sat in crowns and on bishops. It was as precious as anything, because it was purple and there was not much of it.

Then in the nineteenth century enormous deposits turned up in Brazil and Uruguay. Whole cave sized geodes of the stuff. Supply went vertical, the price collapsed, and amethyst was quietly demoted to semi precious, where it has stayed ever since.

Nothing about the stone changed. It is the same mineral, the same colour, the same hardness it had when it was sitting on a crown. The only thing that changed is that we found more of it.

So when you read semi precious, do not read it as a fact about the rock. Read it as a note about what the market thought when the label was printed. Most gemmological bodies have been trying to retire the term for decades, precisely because it tells you nothing about the stone and quite a lot about the person selling it.

Which loops back to the beginning. There is no definition of a gemstone. There is a decision, and it can be unmade.

Questions people ask

Why have I never heard of most of these?

Because the trade is a bottleneck and mineralogy is not. There are thousands of minerals with names and formulas, and jewellery shops carry perhaps thirty. Everything else is real, catalogued and studied, and simply never made it to a display case, usually because it is too soft, too rare to cut, or too fragile to survive being worn. Poudretteite, benitoite and grandidierite are all genuine stones. They are just stones almost nobody gets to sell.

Is a lab grown stone a real stone?

Chemically, yes, and that is not a loophole. A synthetic ruby is corundum with chromium in it, exactly like one out of the ground, and the same tests that identify one identify the other. The difference is history, not substance. One grew slowly under a continent and one grew quickly in a furnace, and the price gap between them is a gap in the story, not in the crystal. Reputable sellers disclose which is which. That is the entire ethic of the business, and it is why disclosure matters more than any test.

Is diamond really the hardest?

The hardest natural material, yes. But hardest is a narrower claim than people think. It means nothing scratches it except another diamond. It does not mean it survives a drop. Diamond has cleavage planes, which are directions the crystal prefers to split along, and a cutter uses exactly that to shape it. Hard and unbreakable are different words and only one of them applies.

Why is jade in here twice?

Because jade is two minerals wearing one name. Jadeite and nephrite are chemically different and were treated as one substance for centuries, because they look alike, feel alike and carve alike, and nobody could tell them apart until 1863. Imperial jade, the green one everyone pictures, is jadeite. Most of the jade carved in China for thousands of years before that is nephrite. Both are correctly called jade, which is a good demonstration of a name outliving the science.

Can I use these for a story or a game?

That is what a lot of people pull them for, and the unfamiliar ones are the best value. A stone nobody has heard of does half your worldbuilding for you, because the reader has no picture to fight with. Look it up before you use it, though. Some of these are soft enough to mark with a fingernail, and a reader who knows will notice.

References

1. Broz, M. E., Cook, R. F. and Whitney, D. L. (2006). Microhardness, toughness, and modulus of Mohs scale minerals. American Mineralogist, 91(1), 135 to 142. https://doi.org/10.2138/am.2006.1844
2. Whitney, D. L., Broz, M. and Cook, R. F. (2007). Hardness, toughness, and modulus of some common metamorphic minerals. American Mineralogist, 92(2 to 3), 281 to 288. https://doi.org/10.2138/am.2007.2212
3. Gerberich, W. W. et al. (2015). Toward demystifying the Mohs hardness scale. Journal of the American Ceramic Society, 98(9), 2681 to 2688. https://doi.org/10.1111/jace.13753
4. Mineralogical Society of America. Mohs Scale of Hardness. https://msaweb.org/mohs-scale-of-hardness/
5. Mindat.org. Mineral and Locality Database. https://www.mindat.org/