Lewis Short
(adjective) : glaesum (glēsum, glessum), i, n. cf. Germ. Glas; gleissen = glänzen, to glimmer; Engl. glass
* Amber, Tac. G. 45; Plin. 37, 3, 11, § 42.—Hence, glaesārĭus, a, um, , of amber, amber-: insula,which produces amber,Plin. 4, 13, 27, § 97; 37, 3, 11, § 42.
Charlton T. Lewis, Charles Short, A Latin Dictionary