noun馃敆ShareA mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO2路nH2O."The geologist carefully examined the opal, noting its beautiful colours but also its softer texture compared to the quartz crystals. "mineralgeologymaterialsubstanceChat with AIVocabulary GamePractice Reading
noun馃敆ShareA colloquial name used in molecular biology referring to a particular stop codon sequence, "UGA.""In her molecular biology class, Sarah learned that "opal" is another name for the UGA stop codon, which signals the end of protein synthesis. "biologybiochemistryChat with AIVocabulary GamePractice Reading
noun馃敆ShareAny of various lycaenid butterflies of the genus Nesolycaena."While hiking in the rainforest, the butterfly enthusiast excitedly pointed out an opal flitting among the ferns. "animalinsectbiologynatureChat with AIVocabulary GamePractice Reading
