Silica in the marine habitat.

A lot of shore line sand and where oceans once existed has silica, that’s a large source of silica that they sand mine to make glass and silicon.
Its shells of algae based plankton over many thousands of years building up that they convert CO 2 from importation in to their shell, and then there is the mineral silica as well.
Silicon valley is supposedly built on an extinct ocean with subsequent abundant silica reserves.