Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos
brittle mica
Introduction References & Edit History Related Topics
Quizzes
Basalt sample returned by Apollo 15, from near a long sinous lunar valley called Hadley Rille. Measured at 3.3 years old.
(Bed) Rocks and (Flint) Stones
Quick Facts
Related Topics:
mica
clintonite
margarite
See all related content
Britannica AI Icon
Adding us as a Preferred Source tells Google you trust our content, so our articles show up more often in your Google Search, Discover feed, and AI Overviews.
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites

brittle mica

mineral
Written and fact-checked by
Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
Britannica Editors
History

brittle mica, any member of the mica group of silicate minerals that has calcium instead of potassium or sodium. The calcium substitution increases the aluminum-to-silicon ratio that enhances hardness. This causes it to break instead of bend. Margarite and clintonite are examples of brittle micas. Both of these minerals occur in metamorphic rocks such as pelitic schists and metasomatized marbles as well as metamorphosed bauxites, basalts, and anorthosites.

This article was most recently revised and updated by John P. Rafferty.