Calcium carbonate can be purchased at "health food" stores. Plain, unflavored calcium antacids might work, it depends on what was used for binding. It is also sold as lime in garden stores, but I have my doubts about the purity.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk