unvitrified pottery.    From Wordnet, Princeton University. 

I consider even the pearlstone as an unvitrified obsidian: for among the minerals in the.    From Wordnik.com.  [Travels to the Equinoctial Regions of America] Reference

I consider even the pearlstone as an unvitrified obsidian: for among the minerals in the King's cabinet at Berlin there are volcanic glasses from Lipari, in which we see striated crystalites, of a pearl-grey colour, and of an earthy appearance, forming gradual approaches to a granular lithoid lava, like the pearlstone of Cinapecuaro, in Mexico.    From Wordnik.com.  [Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1] Reference

The term glastenized glass is employed by Dr. Thompson and others to indicate glass which by slow cooling is wholly unvitrified, and has assumed the appearance of a fossil substance, or real glass-stone.).    From Wordnik.com.  [Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1] Reference

Wedgwood’s pyrometer, yields a glass that softens at fourteen degrees; and that this glass, melted again and unvitrified (glastenized), is fusible again only at thirty-five degrees of the same pyrometer.    From Wordnik.com.  [Travels to the Equinoctial Regions of America] Reference