Iron(II) gluconate, or ferrous gluconate, is a black compound often used as an iron supplement. It is the iron(II) salt of gluconic acid. It is marketed under brand names such as Fergon, Ferralet, and Simron. It is also present in the combination supplement dianazene, a vitamin mixture created by L. Ron Hubbard and used in the religion Scientology. Ferrous gluconate is used as a food additive when processing black olives. It imparts a uniform jet black colour to the olives.