PURPOSE: To easily obtain a food additive containing mineral components such as calcium and magnesium by extracting coral with an aqueous solution of citric acid or acetic acid.

CONSTITUTION: Mineral components such as calcium and magnesium are made to dissolve by immersing coral into an aqueous solution of citric acid or acetic acid. After an acidic taste of the aqueous solution of citric acid or acetic acid is neutralized with alkaline coral and disappeared, the remained solid precipitates are removed. The obtained aqueous supernatant contains calcium, sodium, etc., beside a large amount of magnesium. Further, the powder obtained by drying the removed precipitates contains calcium, magnesium, sodium, etc. Both of these salts are useful as food additives.