The mechanism that creates crystals is movement in the Earth’s crust. As layers of crust float on the liquid rock mantle beneath collisions and pressure create fractures that allow superheated liquids and gases, filled with different elements to move rapidly toward the surface. As these liquids and gases cool. they often crystalize. The temperature, pressure, surrounding rocks and mix of elements all determine which minerals crystallize at a particular place. Crystals and rocks produced in this way are known as igneous.
If crystals and rocks are exposed to wind, frost and water, they begin to erode. Small particles are washed into the sea where they form silt deposits. After many millions of years of extreme pressure, these deposits become compressed, forming sedimentary crystals and rock. Minerals of this type ten to be softer than igneous crystals as they form at lower temperatures and pressures.