This is an enormous, beautifully-formed crystal of translucent hanksite from the type locality in California. From Mineral Galleries: "Hanksite is an unusual mineral mostly because of its formula. It is one of only a handful of minerals that contain both carbonate and sulfate ion groups. This brings up the question: to what mineral class does it belong? Some mineral references place it in the carbonates while others put it in with the sulfates. We have placed it in the sulfate class simply because there are more sulfate groups in its structure than carbonate groups. Hanksite forms very nice crystals in evaporite deposits. These evaporite deposits occur in arid environments. Water, carrying dissolved minerals, floods into a dry lake beds and then just sits. The arid conditions evaporate the water and concentrate the ions. When the water is almost gone, crystals start to form. The mineral halite (salt) is one of the first minerals to crystallize. As the water becomes even more concentrated, eventually rare and unusual minerals such as borax or hanksite will crystallize too." The display side of this giant crystal shows unbelievably good symmetrical form for a crystal this size. The crystal is complete all the way around, with no damage! NOTE: must be kept out of humidity, or in a sealed box, or coated lightly with shellac or mineral oil. 11.1 x 10.2 x 7.3cm