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  • Thanks to Skill Share for sponsoring this episode of SciShow

  • As the pun goes, geology rocks

  • but it isn't all about rocks.

  • Because rocks are usually made of minerals,

  • and minerals are just plain cool in their own right.

  • They have a pretty specific definition, but for the most part,

  • minerals are solid compounds and inorganic elements whose atoms form an orderly, repeating

  • pattern.

  • Geologists have managed to identify over 5000 types of them,

  • and while there's a huge range of abundances,

  • more than half of those 5000 are so rare that they're found in five or fewer places.

  • Those rare minerals aren't things like diamonds or sapphires, either

  • because no offense to your favorite ring, but those are relatively common.

  • Instead, they're things like hazenite and fingerite.

  • They're names that don't make headlines all that often, but form in really cool ways.

  • So this list is our way of celebrating them!

  • Here are 6 of the world's rarest, coolest minerals.

  • That nobody talks about!

  • [INTRO]

  • Okay, I know I mentioned it in the intro, but let's get this out of the way:

  • Despite advertising and pricing to the contrary, diamonds aren't rare.

  • Like, at all.

  • In industry, they're used all the time for their hardness.

  • And even the fancy, gem-quality ones aren't that uncommon

  • instead, their rarity is often manufactured by corporations.

  • That being said, not all diamond gems are equal.

  • They can come in different colors, and some of those colors actually are really rare in

  • nature.

  • Like, you might be familiar with the Hope Diamond at the Smithsonian

  • or that massive, blue rock the old lady dropped into the ocean at the end of Titanic.

  • And blue diamonds are rare.

  • But the /really/ special ones are red diamonds.

  • Most colored diamonds owe their hue to some kind of chemical impurity in their carbon

  • lattice.

  • But in some cases, a diamond's structure gets deformed under high pressure, and the

  • atoms shift around a little bit.

  • That makes some layers of the lattice reflect pink light.

  • And if you get enough of them in a deep enough color, the diamond will come out red.

  • Or at least, that's the leading hypothesis.

  • Scientists still don't fully understand how it works

  • and there is a chance it might have something to do with a nitrogen impurity.

  • Either way, these diamonds are really rare, and we've only found them at a couple of

  • sites in the world.

  • Right now, the main mine is in Australia.

  • It supplies 90% of our pink diamonds, and a tiny fraction of those earn a “red

  • classification from the Gemological Institute of America.

  • The mine sold their first proper red, or technically, their so-calledFancy Red”, in 1999.

  • And as of today, only about 30 small, red diamonds have ever been found.

  • If you've ever browsed through the Tiffany & Company website,

  • you might have seen a gemstone called tanzanite.

  • It's sometimes advertised as being 1000 times more rare than diamonds.

  • Back in the 1960s, Tiffany's became the first company to sell this stone,

  • but tanzanite isn't its real name.

  • Instead, it's called blue zoisite.

  • Now, the mineral zoisite isn't that rare by itself.

  • But the blue variety is.

  • Its color comes from a vanadium impurity

  • in other words, vanadium atoms that got mixed into its crystal structure.

  • And the world's only source for it is a mining area in the Mereani Hills in Tanzania.

  • It's so rare that industry experts estimate the supply will actually run out in a few

  • decades.

  • This supply of tanzanite formed roughly 585 million years ago,

  • due to tectonic activity that would ultimately create Africa's most famous mountain, Mt.

  • Kilimanjaro.

  • Basically, the rocks within each tectonic plate smushed into one another,

  • and under all that heat and pressure, they melted, transformed, and grew new crystals.

  • The exact blend of elements tanzanite is made of came from a mix of these two tectonic plates,

  • as well as any particles carried into cracks by super hot gases.

  • This is why we haven't found it anywhere else.

  • Also, as if tanzanite weren't cool enough just because of how it formed, it has a pretty

  • unique appearance, too.

  • It's pleochroic, which means that its color can change depending on the angle you shine

  • light through it.

  • It happens because vanadium atoms can have different numbers of electrons, which mean

  • they can respond to light a little differently.

  • Rough, untreated tanzanite generally displays blue, violet, and red or brown coloration.

  • If you buy tanzanite jewelry in a store, though, you'll only see the blue-ish colors.

  • That's because the mineral has been heat-treated to make it all pretty

  • so some of the vanadium atoms have changed state and no longer reflect that red light.

  • Now, gems are pretty and all, but most of the rare minerals on Earth just aren't cut

  • out to be gemstones.

  • Many are rare because they can only form under very specific conditions, like combinations

  • of temperature and pressure

  • orin the case of hazenitein extreme pH.

  • Hazenite is only found in Mono Lake, which is in the middle of the California desert.

  • Unlike some of the other examples on our list, it isn't formed from tectonic plates or

  • smushed-together rocks.

  • Instead, it's made by microbes

  • specifically, a group of blue-green algae called lyngbya .

  • One group of researchers proposed that, when the algae die, they release compounds that

  • contain the element phosphorous.

  • Then, that combines with oxygen, along with sodium, potassium, and magnesium in the lake

  • water.

  • And under high pH, that ultimately leads to the formation of hazenite.

  • These crystals come in radiating clusters, ortuftsof long skinny crystals, but

  • they don't even reach half a millimeter long.

  • And also... they dissolve in water.

  • Which is another reason they're really rare.

  • Some news sources call hazenite microbe poop

  • but the scientists who discovered the mineral note that it was found on dried-out or decomposed

  • microbes.

  • And I'm pretty sure that's not quite how poop works.

  • Other minerals get their extreme rarity from being made of a rare element combo.

  • Ichnusaite, for example, was the first mineral discovered that includes both molybdenum and

  • thorium.

  • And if you know anything about thorium

  • yes, that does mean it's radioactive.

  • That by itself isn't that weird, though, because there are actually quite a few naturally-radioactive

  • minerals.

  • Most of them just happen to involve uranium, not thorium.

  • Like tanzanite, ichnusaite gets its name from the only place we can find it

  • the island of Sardinia.

  • actually, the old Greek name for the only place we can find it.

  • Geologists are still trying to figure out exactly how ichnusaite's ingredients came

  • together in that exact spot,

  • but they do have some ideas.

  • For example, the molybdenum could have come from the island's molybdenum-bismuth ore

  • chemically reacting in high-pH conditions.

  • And the thorium could have come from impurities in a type of xenotime

  • which is another mineral also found on Sardinia.

  • Then, somehow, they combined.

  • It's a puzzle researchers are still solving.

  • Also, in the spirit of debunking mineral myths, some places have claimed that only one crystal

  • of ichnusaite has ever been found, but that doesn't seem to be true.

  • In the paper announcing its discovery

  • the researchers reference both a “firstandotherspecimens.

  • So, minerals can be rare because they only form in a few spots, because they form under

  • rare conditions, or because they're made of rare elements.

  • But they can also be labeled as rare because they're hard to get to, like bridgmanite.

  • Bridgmanite is made of elements that are pretty common in Earth's crust: magnesium, iron,

  • silicon, and oxygen.

  • And they're in a ratio that isn't too rare, either.

  • But one specific arrangement of these atoms was hypothesized to only exist deep within

  • the Earth's mantle,

  • where a similar compound breaks down in high pressure and temperature conditions.

  • Down there, it's not found in small quantities, either.

  • Estimates suggest it makes up 38% of the Earth's entire volume!

  • Unfortunately, studies that attempted to find it usually ended in failure, because under

  • relatively ambient conditions,

  • the crystal structure tends to rearrange itself into a random, patternless glass.

  • But in 2014, we finally found some!

  • Just, instead of inside the Earth, it was at the site of a meteorite impact.

  • When that space rock struck the Earth, it created huge amounts of pressure and raised

  • the area's temperature to roughly 2000°C.

  • Exactly the conditions needed to make this mineral.

  • As a bonus, the sample was also encased inside layers of /other/ minerals that kept it under

  • enough pressure to eventually study

  • although we're still waiting to hear any new results.

  • Over the course of this episode, we've talked about all kinds of things that can make minerals

  • rare,

  • from the elements they're made of to the conditions they form under.

  • And if you've been wondering if any mineral checks all four boxesthe answer is yes.

  • Some minerals are the height of rarity, and one of them is fingerite.

  • Which, all things considered, could probably use a more impressive name.

  • Fingerite has only ever been seen near the summit of the Izalco volcano in El Salvador.

  • It's found in fumaroles, or cracks in the Earth's surface from which steam and volcanic

  • gases escape.

  • And it forms when those volcanic gases sublimateor turn directly into a solid

  • and chemically bond with one another at just the right temperature and at just the right

  • ratio.

  • The important elements here are vanadium and copper.

  • If the ratio of these two is off by just a little bit, something other than fingerite

  • forms.

  • And to make things more complicated, it also needs a temperature between 100 and 200°C.

  • But sometimes, it happens, and you get these tiny, opaque black crystals!

  • Yeah, despite the name, fingerite doesn't look too much like fingers

  • it was just named after a guy with the last name of Finger.

  • Either way, this stuff is really rare, and back in the 1980s, scientists had only ever

  • found a few milligrams of this stuff.

  • Some of it is because of the specific conditions it forms under, and also because nobody wants

  • to climb around on an active volcano.

  • But fingerite also dissolves in water, so any time it rains, there goes your sample.

  • With as hard as these minerals can be to find, it seems kind of weird that scientists would

  • devote so much time to searching for them.

  • Like, some of them aren't even that aesthetically pleasing.

  • And you're not gonna make a ring out of fingerite because if you get your hands wet,

  • it will just dissolve.

  • But there is a good reason for it: Minerals like these help us better understand the diversity

  • of our planet.

  • Unlike the other rocky planets in our solar system,

  • Earth has an incredibly complicated variety of minerals.

  • And maybe some of them are related to properties that allow our home to support life.

  • You know, as long as you're not living inside a crack on an active volcano.

  • Or on top of somewhere a bit too radioactive.

  • Basically, don't live everywhere the rare minerals are, okay?

  • One of the coolest things about these minerals is that some of them only last for moment

  • like before a rainstorm.

  • That's why the pictures geologists take of them are so important.

  • If nobody ever photographed things like hazenite, only a few people in the world would know

  • what they look like

  • as opposed to all of you who just watched this video.

  • But thankfully, there are great photographers out there.

  • And if you want to brush up on your photo-taking skills to help share your discoveries and

  • memories,

  • you can try a class from Skillshare.

  • There's one called Fundamentals of DSLR Photography that's really helpful if you

  • want to learn what all of those buttons and dials on your camera do

  • or if you already know the basics and want to learn more.

  • It's taught by Justin Bridges, a photographer out of New York City who's great at sharing

  • and capturing the scenes around him.

  • Skillshare also has more than 25,000 other courses about everything from finance to music

  • so there's a lot to explore.

  • And right now, Skillshare is offering 500 SciShow viewers two months of unlimited access

  • for free!

  • You can check out the link in the description to learn more.

  • [ outro]

Thanks to Skill Share for sponsoring this episode of SciShow

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6 Gems and Minerals Much Rarer (and Cooler) Than Diamonds

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    joey joey に公開 2021 年 06 月 08 日
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