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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OK Boomer can be perceived as pejorative, but it is mostly considered to be _____
Words nearby index mineral
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.