A word for “crystal (white)” (PE17/23) or “silver, shining white” (Ety/SIL) based on the root √SIL “shine (white or silver)”. It seemed to function as both a noun (1950s-60s) and an adjective (1930s), and was the basis for the adjective silivren appearing in the A Elbereth Gilthoniel prayer (PE17/23).
Conceptual Development: Earlier words for “crystal” appeared in the Gnomish Lexicon of the 1910s, such as G. glint (GL/39) and G. sincli (GL/67), both elements in G. Crosailin(t) or Crosincli “Crystal Globe”, a Gnomish name for the Moon.
Neo-Sindarin: For purposes of Neo-Quenya, I would use S. silef mainly as the noun “(white) crystal”, and would use silivren as the adjective form.
_n. _crystal (white). >> silivren