Here’s a great product to grow aragonite crystals just by adding white distilled vinegar. It’s hard to imagine a consumer product with greater social utility.
The packaging contains a seemingly silly warning that:
WARNING: Eating rocks may lead to broken teeth!
Maybe the rocks resemble candy, in which case it wouldn’t be such a silly warning. On the other hand, anyone who would mistake the rocks for candy probably wouldn’t be old enough to read the warning.