A noun appearing as G. glast “marble” in the Gnomish Lexicon of the 1910s (GL/39), probably derived from ᴱ✶ʒalast- like its cognate ᴱQ. alas (alast-) “marble” in the contemporaneous Qenya Lexicon (QL/30).
Neo-Sindarin: I think this word may be salvageable in Neo-Sindarin as ᴺS. glast, reconceived as a derivative of ᴹ√GALAS “joy, be glad”, perhaps from ᴺ✶galast- originally with the sense “thing pleasant to touch”.
An adjective appearing as G. glastrin “marble” in the Gnomish Lexicon of the 1910s, an adjectival form of G. glast (GL/39).
Neo-Sindarin: If adapted to Neo-Sindarin, I think this word would become ᴺS. glathren: compare S. othrond from S. ost + S. rond.