perlite

From French perle (“pearl”) + -ite

perlite (plural perlites)

1. (mineralogy) An amorphous volcanic glass formed by the hydration of obsidian.
2. The lightweight insulating material and aggregate resulting from expanding perlite glass by heat.
   • 1928, Lawrence R. Bourne, chapter 4, in Well Tackled!‎:

     Technical terms like ferrite, perlite, graphite, and hardenite were bandied to and fro, and when Paget glibly brought out such a rare exotic as ferro-molybdenum, Benson forgot that he was a master ship-builder, […]

• Peltier, peitrel, rep-tile, reptile

perla +‎ -lite

perlite f (plural perliti)

1. (mineralogy) perlite

perlite

1. vocative masculine singular of perlitus