Avogadro tells us that we have 6.023 x 10^23 SiO2 units per gram, so there would be 6.023 x 10^23 / 60 ≈ 1 x 10^22 SiO2 units in a gram of pure SiO2, and with SiO2 composed of 3 atoms, that puts us at 3 x 10^22 atoms per gram of SiO2. Now, a grain of sand does not weigh 1 gram. It weighs less
