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Most of the earth's crystals were formed millions of years ago. Crystals form when the liquid rock from inside the earth cool and harden. Sometimes crystals form when liquids underground find their way into cracks and slowly deposit minerals.
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www.rocksforkids.com/RFK/howrocks.html
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Question: How do crystals form? ---Dave Answer: Crystals usually form from molten rock as the molten rock gradually cools. If the molten rock cools very rapidly, then either small crystals form or no crystals form. ... If molten rock cools slowly, then large crystals can form. This happens usually when the molten material...
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www.newton.dep.anl.gov/askasci/gen99/gen99068.htm
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Through these pages you can learn what types of crystals there are, why different crystals have different shapes and sizes, find out how light affects the color of a crystal and how crystals form and how they grow. ... Crystals are solids that form by a regular repeated pattern of molecules connecting together.
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www.chemistry.co.nz/crystals_defined.htm
www.chemistry.co.nz/crystals_defined.htm
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Crystals also can be formed when land masses move. The crust of the earth can buckle and fold, raising mountains and creating new faults. Such stresses create great pressures and temperatures that can change the crystal structures in rocks.
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www.pa.msu.edu/sciencet/ask_st/072094.html
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Tetragonal -- Typically, the crystals are shaped like four-sided prisms and pyramids. Each crystal has three axes, all perpendicular to one another. Two axes are the same length and lie on a horizontal plane. The third axis is not the same length and is at a right angle to the other two.
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www.sdnhm.org/kids/minerals/howto-form.html
www.sdnhm.org/kids/minerals/howto-form.html
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Anthony J. Kim1,3, Raynaldo Scarlett1,3, Paul L. Biancaniello2, Talid Sinno1 & John C. Crocker1 ... Top of page ... Ionic colloidal crystals of oppositely charged particles...
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www.nature.com/nmat/journal/v8/n1/abs/nmat2338.html
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