opal
opal \'o--p*l\ n [L opalus, fr. Skt upala stone, jewel] often attrib : a mineral SiO2.nH2O that is a hydrated amorphous silic a softer and less dense than quartz and typically with definite and often marked iridescent play of colors
Webster's English Dictionaryopal \'o--p*l\ n [L opalus, fr. Skt upala stone, jewel] often attrib : a mineral SiO2.nH2O that is a hydrated amorphous silic a softer and less dense than quartz and typically with definite and often marked iridescent play of colors