Calcium acetate

Calcium acetate is a chemical compound which is a calcium salt of acetic acid. It has the formula Ca(C2H3O2)2. Its standard name is calcium acetate, while calcium ethanoate is the systematic name. An older name is acetate of lime. The anhydrous form is very hygroscopic; therefore the monohydrate (Ca(CH3COO)2•H2O) is the common form.

Calcium acetate can be prepared by soaking calcium carbonate (found in eggshells, or in common carbonate rocks such as limestone or marble) or hydrated lime in vinegar:

Since both reagents would have been available pre-historically, the chemical would have been observable as crystals then.

Pure Ca acetate is yet unknown among minerals. Calclacite – calcium acetate chloride pentahydrate – is listed as a known mineral, but its genesis is likely anthropogenic and it may soon be discredited.[8][9]