Alum Chrom crystal 1.7Kg, under glass

Beautiful purple octahedron (double pyramid) obtained in a laboratory by a clever mixture. It is a Polish engineer who managed to create this big crystal with a block of real granite as a base. This is an Alum crystal from Chrome. A very rare property since by evaporating together a solution of Alum (potassium sulfate) and a solution of Chrome, the two components combine instead of crystallizing separately. It takes a few weeks, but the combination of the two is much more beautiful than the two separate elements. But beware: formed by evaporation, it could disappear if brought into contact with water. so not to touch with his hands...