a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechatelierite
"The geologist explained that while sand is mostly silica, this specific meteorite shard contained a rare crystalline form called lechatelierite."
Silicon dioxide.
"The sand used to make glass is primarily composed of silica, which is silicon dioxide."
The word silica comes from the New Latin term silica, which is derived from the Latin word silex meaning "hard stone" or "flint." This naming followed the pattern used for other chemical compounds like alumina and soda.