This blue stone is anhydrite. It is formed in sedimentary basins where large amounts of sea water have evaporated. It forms itself in layered deposits that can be hundreds of feet thick that usually contain halite, gypsum, and limestone. It presents itself usually as a white or pale blue, glassy surface with a pearly lustre. Perfect anhydrite crystals are rare.
• The name anhydrite comes from the Greek for “without water”,
but when hydrated, it converts to gyspum (CaSO ·H O). If the 42
gypsum is heated up to around 200 °C (400 °F,) it will release the water previously absorbed and convert back to anhydrite.
• This variety of anhydrite is called angelite, and is specific to Lima, Peru.
• Anhydrite is a 3.5 on the Mohs hardness scale, similar to a copper penny.
• Anhydrite’s hydrating property is key to the manufacturing of plaster of paris and cement.
• Add anhydrite to your geology collection
MEASUREMENTS: 2" and up
You will receive a specimen similar to those shown in photos.