Anorthosite main content.


Part of Hall of Planet Earth.


Exhibition Text

This is an anorthosite, composed almost entirely of plagioclase (white).  Pyroxene occupies the spaces between the plagioclase crystals.  Although several thick layers of anorthosite exist in the Stillwater Complex, these rocks are rare, and how they form is poorly understood.

AMNH collection

For Educators

Topic: Earth Science

Subtopic: Earth Structure

Keywords: Intrusions (Geology), Plagioclase, Pyroxene, Stillwater County (Mont.), Anorthosite

Audience: General