index mineral

American  

noun

• index minerals
  plural

1. Geology. a mineral which is only formed under certain temperature and pressure conditions, which when found in metamorphic rock gives information about the conditions under which that rock formed.

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index mineral Scientific  

1. A mineral that forms only under specific pressure and temperature conditions, and that therefore provides information about the metamorphic history of the rock in which it is found. The minerals kyanite, andalusite, and sillimanite are examples of index minerals.

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Other Word Forms

Noun Inflected Forms

• index minerals
  plural

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Example Sentences

See Examples For:

index mineral

Garnet schist includes the high-grade index mineral garnet and indicating it has experienced much higher pressures and temperatures than chlorite.

From Textbooks ● Jan. 1, 2017

Chlorite schist includes the low-grade index mineral chlorite.

From Textbooks ● Jan. 1, 2017

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