Mineral crystals form at the surface and deep within the Earth. They grow from vapors that contain plenty of mineral components. Many crystals form in volcanic locations where hot gases encounter cool temperatures.
Most mineral crystals form in molten rocks. They are created close to each other when magma cools, and they are produced in irregular shapes. Some crystals have a cube shape, while others have triangle shapes. Perfect crystals show straight edges, such as the cubes of salt. However, most crystals do not have perfect shapes. This is due to the fact that crystals grow in confined spaces in the ground and do not have adequate space to form evenly in all directions. Some crystals appear to have straight edges in some parts but rounded or jagged in other areas.
Solutions rich in minerals found in spacious rock cavities produce large and well-formed crystals. Crystals start to grow on rock walls, on other crystals and on dust particles when solutions become fully saturated with mineral components. The length of time it takes crystals to form varies depending on the concentration of the solution and temperature changes. Some crystals form in a few minutes, while others take thousands of years to grow.