• Introduction
Gypsum is one of the more common minerals in sedimentary environments. Gypsum crystal is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.

• Properties
- Color is usually white, colorless or gray, but can also be shades of red, brown and yellow.
- Luster is vitreous to pearly especially on cleavage surfaces.
- Transparency crystals are transparent to translucent.
- Crystal System is monoclinic; 2/m
- Cleavage is good in one direction and distinct in two others..
- Fracture is uneven but rarely seen.
- Hardness is 2 and can be scratched by a fingernail.
- Specific Gravity is approximately 2.3+ (light)
- Streak is white.
- Associated Minerals are halite, calcite, sulfur, pyrite, borax and many others.
- Other Characteristics: 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.
- Notable Occurances include Naica, Mexico; Sicily; Utah and Colorado, USA; and many other localities throughout the world.
- Best Field Indicators are crystal habit, flexible crystals, cleavage and hardness.