Crystals Lesson for Kids: Definition & Facts

Instructor: Kathryn Miedema Dominguez

Kathryn has taught elementary students for over ten years and has her master's degree in elementary education.

Crystals are not just diamonds, but unique formations of stacked atoms. Many crystals are made of minerals, but there are other types of materials that also make crystals. In this lesson, you will learn about what a crystal is, the types of shapes, and how they are formed.

What are Crystals?

What do snowflakes, table salt, and pencil lead all have in common? They are crystals. A crystal is a solid formation that follows a pattern as it shapes things such as salt, sugar, or emeralds. Although most people think of gems and diamonds as the only kind of crystals, they can be made of various materials. However, many crystals are made of minerals.

If you were to look at a single grain of salt under a microscope, you would see the unique shape of a cube. Salt is a mineral, and when found in nature it's called halite. A mineral is a non-living natural substance from the earth.

Salt is a cubic crystal.
grain of salt

When minerals become solid, they create a specific shape based on how their atoms are stacked. Atoms are the smallest parts of something. Imagine a cookie crumbling apart. All the crumbles are atoms, and when put back together, they form a cookie. Everything is made of teeny-tiny atoms that can only be seen with a microscope.

When a crystal forms, all the little specks of the mineral connect with each other like Legos. But unlike Legos, when minerals form crystals, they make a shape that has a pattern. In addition, every mineral makes a different shape because their atoms are different.

It's All About The Shape

One of the most important aspects about classifying a crystal is by its shape. The shape has to be three-dimensional, and the atoms have to create a repeating pattern to form it. There are seven main groups of crystal shapes:

  • Cubic crystals are shaped like a cube and can have up to 12 sides.
  • Hexagonal crystals have six sides.
  • Trigonal crystals have three sides.
  • Monoclinic crystals look like a diamond-shaped box with many sides.
  • Orthorhombic crystals are shaped like a rectangular prism (rectangular box).
  • Tetragonal crystals are also like a rectangular prism, but one side is longer.
  • Triclinic crystals look like slanted rectangular prisms because they don't have 90° angles.

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