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index mineral

American  

noun

plural

index minerals

  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.

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.

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.