Ammonia Alum

(NH4)Al(SO4)2.12H,O. Made by bring Ammonites: 1, Ammonites obtusus ; 2, section of Ammonites obtusus , showing the interior chambers and siphuncle; 3, Ammonites nodosus . chambers are plaited where they meet the shell, so as to form at the junction exceedingly intricate and beautiful patterns, which are characteristic of the genus.