[dehrmann]

It's better than that. According to Wikipedia

> Chalk is typically almost pure calcite, CaCO3, with just 2% to 4% of other minerals

The supplement I just looked up uses Calcium Carbonate. That could just be purified chalk and be in compliance with the FDA. In fact, it probably is just that.

[beambot]

Animals eat naturally-occurring chalk (and other substances) to regulate key minerals. It's called geophagia.

[dehrmann]

https://en.wikipedia.org/wiki/Mineral_lick

[FredPret]

> geophagia

Animals are eating the world