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Phosphorescence

The residual emission of absorbed energy in the form of light by a substance, following exposure to incident radiation

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Phaneritic

A term for igneous rocks having a texture of grainy crystal visible to the naked eye

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Phase

The sum of homogenous material within a larger heterogeneous material body

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Permian period

The period 280 to 245 million years ago, followed by the Mesozoic era. Known as the age of amphibians

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Petrification

The replacement of minerals in organic matter by calcareous, carbonaceous or siliceous minerals, which serve to solidify and preserve the form of the matter beyond its organic state

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Permafrost

A depth of the earth’s surface or subsurface which is permanently frozen.

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Peridotite

Intrusive igneous rock formed within olivine, the source of Peridot

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Pillar

A solid block of rock used to support a mine shaft