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TITLE: How Do Crystals Grow?


[Photo: Volcanic Vent]
New mineral crystals are always forming — at the surface and deep within the Earth. Crystals can even grow from vapors rich in mineral components. This happens most commonly in volcanic areas where hot gases encounter cool surroundings and deposit crystals. This photograph shows sulfur forming near a volcanic vent in Java, Indonesia.



Most mineral crystals grow from molten rock deep within the Earth. As a magma cools, many crystals form simultaneously and crowd into one another, producing irregular shapes. In this rock slab, quartz and feldspar crystallized to form the speckled granite.

  [Photo: Magnified Surface of Granite]

Why are the crystals of this quartz so large and well formed? Because they grew out of mineral-rich solutions in spacious rock cavities. When solutions are completely saturated with mineral components, crystals can begin to form on rock walls, on other crystals, or even on particles of dust. They can grow quickly or slowly — or even stop — depending on changes in temperature and the concentration of the solution.

  [Photo: Quartz Crystal]

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Smithsonian National Museum of Natural History Department of Mineral Sciences website Credits