Pearlite
Pronunciation : Pearl"ite, Pearl"stone`
Part of Speech : n.
Definition : Defn: A glassy volcanic rock of a grayish color and pearly luster, often having a spherulitic concretionary structure due to the curved cracks produced by contraction in cooling. See Illust. under Perlitic.
(Min.)
Source : Webster's Unabridged Dictionary, 1913