When you think about the materials  that make our modern gadgets work, you probably imagine metal wiring,  or maybe silicon circuit boards.

You probably don’t think about gemstones. Precious crystals may look beautiful  in your collection or on your wrist, but that’s where the usefulness  of many of them ends.

However, tourmaline is one of the exceptions. Under certain conditions, this  mineral really is electric. [♪ INTRO] Tourmaline is a kind of stone called  a crystalline silicate mineral. Actually, it’s a whole group of them, since there’s a lot of variety in what elements  can be included in their crystal structure.

The needle- or prism-shaped crystals of  tourmaline are forged, like many of Earth’s finest gems, under some of the most  extreme conditions our planet has to offer. And tourmaline comes in a range of colors. In fact, it’s one of the most  colorful gemstones in the world, covering everything from pinks and  greens, to blue, and even black.

Some of the most remarkable examples  contain multiple colors in a single crystal. There’s even a tasty looking variety  called watermelon tourmaline, with red and green sections  separated by a band of white. All of this diversity is possible because of  tourmaline’s unique silicate crystal structure, which acts a bit like a cage, trapping  different mineral ions inside.

That produces the different colors. For example, high concentrations of  iron will give you black tourmaline. But in lower amounts, that same iron  results in blue or green crystals.

Manganese ions make pinks, chromium makes green, copper makes intense blue, and  vanadium gives you yellows and browns. Now, tourmaline was first described in  Ceylon—the island that is now known as Sri Lanka—and the name comes from the  local word meaning “stone of mixed color”. But some people also referred to  the gem as the Ceylonese magnet.

Sometimes, if the concentration of iron  is high enough in a tourmaline crystal, it can become slightly magnetic, but this  isn’t actually the reason for the nickname. Because regardless of the mineral ions  trapped inside, when a crystal of tourmaline is heated up, it can produce an electric charge that can attract or repel other charged  objects, just like a magnet would. The effect is known as pyroelectricity.

This bizarre phenomenon was first documented by the ancient Greek philosopher  Theophrastus, more than 2300 years ago. But it wasn’t until the 18th century that  scientists started to really experiment with the electric properties of gemstones. One of those experiments  showed how tourmaline crystals could attract hot ashes, while  leaving cold ashes unaffected.

And reading up on the early experiments  gave the SciShow team an idea, but we’ll get to that in a minute. By the middle of the century, the  famed taxonomist Carl Linnaeus began to relate this mineral  behavior to electricity. And brothers Paul-Jaques and Pierre  Curie discovered that it wasn’t only heat that could persuade crystals to be  electric, but also mechanical stress.

They had identified piezoelectricity. If you squeeze a crystal to subtly change its  shape, it can generate an electric charge. And the inverse is true as well  - running an electric current through a crystal would make it change its shape.

The key to this seemingly  magical effect is in the way the atoms are arranged in the crystal. And while this happens with a few  other materials besides tourmaline, we’ll use it as our example. The basic component of a tourmaline  crystal is silicon dioxide.

Silicon dioxide molecules form a  tetrahedral, or four-sided, shape. For you tabletop RPG nerds, it’s the  shape of a D4, or a four-sided die. And while this is pink, it is not tourmaline.

It is plastic. They’ve got their silicon in the middle  and an oxygen atom at each corner. Those pyramids are all lined up in rows  within the crystal, all pointing the same way.

But the bonds between silicon  and oxygen are unequal, and oxygen is more greedy  with its share of electrons. So the bases of the silicate pyramids end up with a slight negative charge,  compared to their tips. Now normally, this is balanced out  by positively charged metal ions between the rows of tetrahedra, the same  ones that give the tourmaline its color.

So a crystal sitting on your shelf  won’t have a net charge to it. But when you squeeze that crystal along its  axis, the negatively charged pyramid bases and the positively charged  ions get pushed together. The balanced ‘center of charge’ gets  separated, with the negative charges pushed a little bit one way, and the positive  charges pushed a little bit the other way.

So you end up with a net positive charge  at one end and a net negative charge at the other, which creates an  electric voltage, just like a battery. Squeezing or stretching the  material can have this effect, but so can heating or cooling it, because heating something up makes it  expand, and cooling it makes it contract. Stretching or heating the material makes the spaces between the tetrahedra expand offsetting the center of charge in the other direction, and creating positive and negative  charges at opposite ends of the crystal.

The piezo- and pyroelectric  effect has since been found in many other materials as well as tourmaline,  including quartz crystals and even bones. Today, a surprising number of our gadgets  rely on piezo- and pyroelectricity, too. These electric materials don’t  need any external power sources, since they get all the  voltage they need from inside.

Everything from infrared heat sensors,  quartz watches, inkjet printers, and even barbecue lighters  and musical greetings cards, can have piezo or pyroelectric materials in them. But, there’s a downside, since tech  that relies on piezo- or pyroelectricity can be very sensitive to  changes in their environment. Today, our gadgets don’t  typically use tourmaline crystals, but rather lab-made or more abundant  natural piezoelectric materials.

But that doesn’t make the effect any less magical. And SciShow Rocks Box  subscribers, more on that later, can play with pyroelectricity when they  receive this month’s mineral, tourmaline! Remember how I said those old  experiments gave us an idea?

Well, here’s how to recreate the original  Ceylonese Magnet demonstration right at home. It’s experiment time! Here’s what you need: A fire-safe container  with a lid, tissue paper, matches or a lighter, tweezers or tongs, some water,  and of course, tourmaline.

Now, a quick note: We’re going  to be playing with fire here, you know, like literally playing with fire. So please, be careful! You want to wear close-fitting  sleeves, and tie back long hair.

Set up your whole experiment in a clutter-free  area with lots of space around you. If you’re inside, make sure there’s  no curtains or flammable stuff around, and if you’re outside, pick a spot away  from structures or flammable materials. And if you get nervous about the fire, just cover your container  with that lid and step away.

Covering it up will smother the flames. Okay, now to the fun part! Rip up a bunch of your tissue paper, toss  it into your container, and let ‘er rip!

Safely, of course. Watch it closely to make sure no  embers float out of your dish! Once all the flames are 100% out, pick  up your tourmaline with the tweezers.

Hold it close to one end, like this! You want to hover the crystal right over  some of the hot ashes, without touching them. If you aren’t seeing anything right away, try  flipping it around and using the other end.

Since the crystal has a  positive and negative side, one end will be more inherently  attractive than the other. You can try this with more than  one piece of tourmaline, too, which means you can test if one of  them works better than the other. When you’re done playing around, the last step is to fill your dish with water  and make sure the ashes get good and wet.

This is to make sure the fire is 100% out, because we here at SciShow do not  want you to set your house on fire. If you give this a try, let us know. And if you don’t know where to get tourmaline, you can get some in this  month’s SciShow Rocks Box.

Every month, SciShow Rocks  Box subscribers will get a rock, mineral, or fossil  delivered to their house, where they can put it on their shelf, or  wherever they put their rock collections. Mine goes on my shelf. We have a limited number of boxes every month  and they generally sell out pretty fast.

So if you would like to subscribe, you can go to SciShow. Rocks. Thank you so much for watching.

Now, go! Really. SciShow.

Rocks. Go! [♪ OUTRO]