A World of Crystals


We live in a world of crystals. The rocks that make up the planets in our solar system, including our own, are made of minerals. These minerals are composed of various elements and normally occur naturally in crystal form. Sometimes the rocks themselves have crystalline structures, too. More commonly, rocks have polycrystalline structures and are made of aggregated materials that contain tiny crystallite grains.

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This slice of the Esquel meteorite is billions of years old and is composed of an iron and nickel core with peridot crystals. “Esquel” by Doug Bowman is licensed under CC By 2.0

Some of the best-known examples of crystals are gemstones. Volcanoes bring up diamonds and rubies that form miles beneath the earth’s surface when they erupt.

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“Ruby” by Jarno is licensed under CC By 2.0

Crystal particles also make up our mountains and form the ocean floor.

You don’t have to search far and wide to find crystals, however. When you walk across playground sand, you are walking on crystals. Did you ever wonder where the black sand comes from? Try to pick it up with a magnet. It will stick to the magnet because it is a mineral, a metal, and probably iron.

Our homes, too, are made of crystalline and polycrystalline materials, like natural rock. Even artificial materials, like cement, get their strength from the growth of crystal particles.

Rocks, pebbles, sand, and dust are all formed from eroded crystals. Like the rock they come from, these particles stay in the same crystal form even as they get smaller and smaller, even as they become dust in the air.

The world of crystals even extends into living things. Kidney stones plague many animals. Kidney stones found in dogs, cats, horses, and people may be composed of struvite, a naturally occurring crystal.

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“Struvite under the microscope” by SuSanA Secretariat is licensed under CC By 2.0
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The crystalline structure of this gallstone is visible to the naked eye. “Epekő (Gallstone)” by Szalai Istvan is licensed under CC By 2.0

Ever wonder why a pearl gleams in the sunlight? When a particle of sand gets caught in an oyster’s insides, it secretes a fluid around the sand. Like a scab on a skinned knee, this secretion protects against infection. This fluid, however, is rich in a crystalline mineral called aragonite. Over many years, the layers upon layers these tiny crystals form around the sand become what we know as a pearl. This layering of aragonite gives the pearl the shine everyone loves.

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A pearl is a kind of crystalline scab, an aragonite bandage for an oyster.

Even our bones and teeth are part crystal. The crystalline mineral apatite is a principal part of our enamel and bones.

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“Apatite” by Kevin Walsh is licensed under CC By 2.0

Crystals are all around us. From mountains to bones, from diamonds to kidney stones, our world of crystals is vast and exciting.