Name: How do crystals work? - Graham Baird
Uploaded: 2020-04-15T16:17:42.000Z
Duration: 5 min 7 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Deep beneath the geysers and hot springs  of Yellowstone Caldera

lies a magma chamber produced by a  hot spot in the earth's mantle.

As the magma moves towards  the Earth's surface,

it crystallizes to form young,  hot igneous rocks.

The heat from these rocks drives  groundwater towards the surface.

As the water cools, ions precipitate out  as mineral crystals,

including quartz crystals from silicon  and oxygen,

feldspar from potassium, aluminum,  silicon, and oxygen,

Many of these crystals have signature  shapes—

take this cascade of pointed quartz,  or this pile of galena cubes.

But what causes them to grow into these shapes again and again?

Every crystal's atoms are arranged  in a highly organized, repeating pattern.

This pattern is the defining  feature of a crystal,

sand, ice, sugar, chocolate, ceramics,  metals, DNA,

and even some liquids have  crystalline structures.

Each crystalline material's atomic  arrangement

falls into one of six different families:

cubic, tetragonal, orthorhombic,  monoclinic, triclinic, and hexagonal.

that reflect the arrangement  of their atoms.

Take galena, which has a cubic structure  composed of lead and sulfur atoms.

are arranged in a three-dimensional  grid 90 degrees from one another,

while the relatively small sulfur atoms  fit neatly between them.

As the crystal grows, locations like these attract sulfur atoms,

while lead will tend to  bond to these places.

Eventually, they will complete the grid  of bonded atoms.

This means the 90 degree grid pattern  of galena's crystalline structure

is reflected in the visible  shape of the crystal.

Quartz, meanwhile, has a hexagonal  crystalline structure.

This means that on one plane its atoms  are arranged in hexagons.

In three dimensions, these hexagons are  composed of many interlocking pyramids

made up of one silicon atom  and four oxygen atoms.

So the signature shape of a quartz  crystal

most crystals have the potential to form multiple geometric shapes.

For example, diamonds, which form deep in the Earth's mantle,

have a cubic crystalline structure and can grow into either cubes or octahedrons.

Which shape a particular  diamond grows into

depends on the conditions where it grows,

including pressure, temperature,  and chemical environment.

While we can't directly observe growth  conditions in the mantle,

laboratory experiments have shown some evidence

that diamonds tend to grow into cubes at  lower temperatures

Trace amounts of water, silicon,  germanium, or magnesium

And diamonds never naturally grow into the shapes found in jewelry—

those diamonds have been cut to  showcase sparkle and clarity.

Environmental conditions can also  influence whether crystals form at all.

That's because glass cools  relatively quickly,

and the atoms do not have time to arrange themselves

into the ordered structure  of a quartz crystal.

Instead, the random arrangement  of the atoms in the melted glass

Many crystals don't form geometric shapes

because they grow in extremely close  quarters with other crystals.

many minerals within it crystallize at the same time and quickly run out of space.

don't grow into any discernible geometric shape in most environmental conditions,

Every crystal's atomic structure has  unique properties,

and while these properties may not have any bearing on human emotional needs,

they do have powerful applications  in materials science and medicine.

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How do crystals work? - Graham Baird

potential

eventually

extremely

material