(RM) How Minerals Form Lesson

How Minerals Form

Minerals form as hot magma cools inside the crust, or as lava hardens on the surface. As magma cools, the atoms lock into place forming crystal structures. Several factors will determine the size of the crystals that form. If the crystals form slowly during cooling they will form in large crystals. Slow cooling most often occurs when the magma remains deep below the surface. If the magma cools quickly smaller crystals will form. Magma closer to the surface will cool faster. The amount of gas the magma contains, and the chemical makeup of the magma will determine the chemical makeup of the minerals. When magma erupts to the surface, becoming lava, the lava will cool quickly and form minerals with small crystals.

Silicon and oxygen, the two most common chemical elements in the Earth's crust, combine as silicon dioxide to form the mineral quartz. Quartz is the most abundant mineral in the Earth's crust. Quartz has been found in meteorites and in some rocks collected on the moon.

Quartz has the chemical formula SiO₂. There are many varieties of quartz, which occurs in nearly all types of igneous, metamorphic and sedimentary rocks. It is an essential mineral in granites, granodiorites and rhyolites. Metamorphism of quartz-bearing igneous and sedimentary rocks typically increases the amount of quartz and its grain size.

In general, minerals can form in two ways:

Through crystallization of melted materials
Through crystallization of materials dissolved in water

CRYSTALLIZATION: the process by which atoms are arranged to form a material with a crystal structure.

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