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    Home / Science lessons / Learn About Crystals
    • Learn About Crystals

      Learn About Crystals

      What Are Crystals?

      A crystal is a hard, solid substance made of molecules that bond together in specific patterns to form an interesting shape that has straight edges and flat surfaces. Not all crystals have the same shape, as you can see in the salt vs. sugar project - there are actually lots of different kinds of crystals, and each kind has its own special shape. Some crystals that you are probably very familiar with are sugar, salt, and ice. But many other solids are made of crystals too; we just can't see them because they are so small! Lots of minerals form beautiful crystals that are used for jewelry, like diamonds or emeralds. Crystals are often transparent, which means that you can see through them sort of like you can see through glass. Other kinds have beautiful colors.

      What Are They Made Of?

      What a crystal is made of actually depends on what kind of crystal it is -- for example, salt, sugar, and snowflakes are actually formed out of different kinds of crystals! Snowflakes are made from crystals formed by frozen water. (You can see a picture here.) Salt crystals are formed by some chemical elements -- sodium and chlorine -- which join together in a crystal shape. (You can see a picture of salt crystals here.) Sugar crystals and rock crystals are made up of different chemical elements, too.

      A geode is a rock with crystals formations insideCrystals can be formed in several different ways. Most crystals are formed through evaporation. For example, when water from saltwater evaporates (or is dried up into the air), salt crystals are left behind (do the Borax Snowflakes project to see this happen). Ice crystals are formed when water from the Earth evaporates into the air and becomes a gas called water vapor. The water vapor becomes clouds and then freezes and falls back down to earth as snow. Ice crystals can also form as frost on windows and on the ground when the air has a lot of moisture (water vapor) and the temperature is below freezing. Some types of crystals are formed from melted rock in the earth (remember this from when we talked about Volcanoes?). When the hot rock cools gradually, it will sometimes form crystals. Geodes are round rocks that are formed when bubbles are trapped in the melted rock. As the bubbles cool down, crystals grow inside of the bubble of rock!

      Crystal Shapes

      As a crystal grows, the pattern that makes it a certain shape will be repeated over and over, so the crystal will always keep the same shape as it gets bigger! The chemical elements that a crystal is made of are what tell the crystal what shape it will be. A crystal of salt is a different shape than a crystal of sugar (do the Salt vs. Sugar project to see for yourself!) because they are both formed from different elements. A lot of crystals might seem to look alike at first glance, but what elements the crystal is made out of will make it a unique shape and color. Even the same element can make different crystals, though, based on conditions such as temperature and light and what other elements are around. For example, the graphite used inside of pencils is a kind of crystal made from the element carbon, which is actually the same element that diamonds are formed from!

      Ways Crystals Are Used

      • Many types of crystals are very beautiful to look at and are used to make jewelry. Diamonds, sapphires, amethysts, and rubies are all types of crystals that are often used in jewelry such as rings, earrings, and necklaces. Oftentimes the crystals will be cut into "gemstones" to make a more smooth shape and to make them fit onto the jewelry.
      • Crystals from rocks called quartz are used inside of computers, radio transmitters and receivers (the things that allow radios to send and pick up sound), and in watches. Energy can flow through certain kinds of crystals so that they can make watches work to keep time and radios pick up signals and send them to speakers so you can hear them!
      • LCDs ("liquid crystal display") like television screens and computer monitors actually use a certain type of crystal too - but it's very different from most crystals because it is more like a liquid than a solid! Even though it is a liquid, its molecules arrange themselves in a pattern, just like they would in a solid crystal. That's why it's called liquid crystal.

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    By: emily
    Date: Dec 10, 2015

    This was really amazing. It helped me with my science fair project. I am trying to find out if crystals grow better in freshwater, saltwater, or water with iodized salt. We’ll know soon!!! I’ll have to tell you guys when the results come in… I’m thinking salt but we’ll see!!!

    By: Izzy
    Date: Nov 15, 2015

    My friend and I are doing a science project and we needed background information about crystals and this really helped me! Thank you so much!! we got an A. :)

    By: Chentian
    Date: Oct 15, 2015

    I really like the interesting facts that has written down the page
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    By: jane
    Date: Oct 12, 2015

    thanks I really needed the information for my science fair project. who ever wrote this did an amazing job. thanks again!!!!!

    By: Haley
    Date: Oct 08, 2015

    I thought it could use a section on how to cite this web page, but other than that, it helped me alot! Thank you!

    [HST adds:  Check out our FAQ!  Here is a typical format for online articles:

    “What is the Scientific Method?” Home Science Tools. Accessed 21 September 2012

    Hope this helps!]

    By: lally
    Date: Jun 15, 2015

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    Date: Jun 11, 2015

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    Date: May 19, 2015

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    Date: Mar 27, 2015

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    By: Kennedy
    Date: Mar 24, 2015

    I thought it was helpful. But I would like to know more about what features do they have, what scale of hardness are they on, and just a little more details! Other than that it helped me for a drawing project I’m doing since im a artist!