. . . "These bits are indeed small on a human scale - the average Zircon used in dating is only about 0.2 millimeters in diameter.But that is still a huge number of atoms.1/250,000 cm3 at Zircon's density of 5.7 g/cm3 is about 22 micrograms.At a molecular weight of 123, that is ~0.15 micromoles, and at three atoms per molecule that is around 280,000,000,000,000,000 atoms.Of course most of the atoms are o" .