Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos
porcellanite
Introduction References & Edit History Quick Facts & 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
Also spelled:
porcelanite
Related Topics:
chert and flint
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

porcellanite

rock
Also known as: porcelanite
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

porcellanite, hard, dense rock that takes its name from its resemblance to unglazed porcelain. Frequently porcellanite is an impure variety of chert containing clay and calcareous matter; when of this nature it is composed chiefly of silica (see chert and flint).

The porcellanite of some authorities is a silicified tuff, a rock composed of volcanic fragments that has been altered to silica, or even metamorphosed marl, calcareous rock fragments altered by heat and pressure (see also hälleflinta). One porcellanite, common in lignite deposits, is formed from the fusion of shales and clay on the floor, walls, and roof of burned coal seams.