: thin crystals are flexible but not elastic, meaning they can be bent but will not bend back on their own. Also some samples are fluorescent. Gypsum has a very low thermal conductivity (hence it’s use in drywall as an insulating filler). A crystal of Gypsum will feel noticeably warmer than a like crystal of quartz.
: halite, calcite, sulfur, pyrite, borax and many others
: include Naica, Mexico; Sicily; Utah and Colorado, USA; and many other locallities throughout the world
Best Indicators : crystal habit, flexible crystals, cleavage and hardness