tridymite
Trid"y*mite, n. Etym: [Gr. (Min.) Defn: Pure silica, like quartz, but crystallizing in hexagonal tables. It is found in trachyte and similar rocks.
Trid"y*mite, n. Etym: [Gr. (Min.) Defn: Pure silica, like quartz, but crystallizing in hexagonal tables. It is found in trachyte and similar rocks.