[opal] n [L opalus, fr. Gk opallios, fr. Skt upala stone, jewel] (1591): a mineral that is a hydrated amorphous silica softer and less dense than quartz and typically with definite and often marked iridescent play of colors
OPAL
Meaning of OPAL in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012