isopyre

[ ahy-suh-pahyuh r ]
/ ˈaɪ səˌpaɪər /

noun Mineralogy.

an impure variety of opal, containing alumina, lime, and iron sesquioxide.

Origin of isopyre

1820–30; iso- + Greek pŷr fire
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019