Over 90% of the Earths crust is
silicate material.The covalent silicate
structures are very strong but they do break slowly under carbonic acid
attack to generate the hard to characterise silicon
hydroxide or silicic
acid.H4SiO4= Si(OH)4
[SiO44-](s)+ 4H+®Si(OH)4(aq)
•Silicic acid is
involved in silicon cycling in the oceans where marine phytoplankton (diatoms) incorporate amorphous silicon oxides in their cell walls.