fiamma

plural fiamme

1. geographyA "flame structure" found in welded ignimbrite and tuff: a small, dark lens of glassy material (possibly pumice which was compressed or collapsed during welding).

   […] black glass from "fiamma" of ignimbrites from Zavaritzkiy caldera in Simushir Is.

   1966, Bulletin Volcanologique, page 88

   3 more examples

   […] the largest fiamma in the centre of the photograph has responded in a brittle fashion to […]

   1993, Jocelyn McPhie, Mark Doyle, Rodney Leslie Allen, Volcanic Textures: A Guide to the Interpretation of Textures, page 135

   […] lenticular "fiamme" of dense black glass. In (d), devitrification has produced radiating spherulites that have grown outward from centers around phenocrysts and across the original shards of glass.

   1993, Alexander R. McBirney, Igneous Petrology, page 359

   […] total phenocryst content in fiamme of pyroclastic rocks and in matrix of coherent rhyolitic rocks; data see Tables 1 and 2; (d) aspect ratio v. maximum particle size (mps) of fiamme (note: this diagram shows field measurements not presented in tables […]

   2008, Kenneth Thomson, Nick Petford, Structure and Emplacement of High-level Magmatic Systems, page 214