Because SiO2 is one of the most stable minerals known, whereas copper and iron (and their oxides) are not; they readily chemically and biologically available an

Because SiO2 is one of the most stable minerals known, whereas copper and iron (and their oxides) are not; they readily chemically and biologically available and will be dealt with by the body. Keeping iron from dissolving is hard Dissolving SiO2 is nearly impossible (one of the many great advantages SiO2 brings in Si in lithograpjy). EDIT: You can do these experiment at home! Buy very fine iron wool and some fiber glass. The giber glass is a stand in for asbestos. Warning! these experiments involve fire or the evolution of corrosive fluids. Blow torch the iron and glass wool. How do they fare? WARNING! This fire is very hard to put out. Mix bleach with iron wool and glass wool. Mix vinegar. Note, for best results use organic apple vinegar with the mother, or a too shelf Japanese rice vinegar Mist the iron wool and the fiber glass with water. RESULT: In all these experiments glass was unfazed. Iron didn't make it in any. Sometimes violently.