Changing Rocks and Minerals

Any rock, whether igneous, sedimentary or metamorphic, can be changed through metamorphosis. The minerals that form will depend on the composition of the original rock, the amount of heat and pressure, the fluids available to help crystallisation, and the time for the process to happen.

A rock formed by metamorphism will usually look very different from the original. Rocks with unusual chemical compositions may produce rare and unusual minerals. The number of chemical ingredients in a rock determines the variety of minerals than can form.

Water is squeezed out of pores and cracks in rocks as they are buried and compacted. Water and gas are also released by minerals as they break down during metamorphism. These ‘juices’ may mix and carry chemical ingredients through the rocks, forming a range of interesting minerals.

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