1. A fine-grained quartzite used to line refractory furnaces.
2. A mixture of fire clay and ground quartz, used to line metallurgical furnaces.

[Origin unknown.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.