Dan Abel wrote:
>
> Silicon Dioxide is sand. I'm sure it is finer than sand at the beach.
> It keeps the salt from clumping.

It's most likely fumed silica, which is commonly used
as a glidant in handling powders. Fumed silica is
produced by the flame process from silane tetrachloride
gas.

It's not sand. Sand is crystalline silica, while
fumed silica is amorphous.