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Gypsum
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Gypsum

You can find gypsum in sedimentary rocks, deserts, and caves. Large amounts can form in layers on a salty sea or lake bottom when water evaporates leaving the mineral behind.

Gypsum sometimes forms when water evaporates in sandy areas like deserts. The gypsum crystals can trap sand grains as they grow. This makes the crystals the same color as the sand. Sometimes the gypsum crystals with their trapped sand grains form a shape called a Desert Rose.

Gypsum crystals are a little bit flexible. That means that thin crystals can bend a little bit. Bend them too much however, and they will break apart.

There is probably some gypsum in your house and school! Gypsum is used in building materials like plaster and sheetrock.

  • Shape: Monoclinic (often forms thick tabular or prism shaped crystals)
  • Luster: Pearly
  • Color: White, yellowish, or brown
  • Streak: White
  • Hardness: 2 on Mohs Hardness Scale
  • Cleavage: Perfect in one direction, poor in another direction
  • Fracture: Thin elongate fractures

Last modified June 12, 2003 by Lisa Gardiner.

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TES XXVI, 3 fall 2010 The Fall 2010 issue of The Earth Scientist, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!

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