Mini Me Geology Blog

Gypsum is one of the most unique minerals found in the world with beautiful samples forming in numerous countries and settings. Some minerals, like gypsum, have the fascinating ability to take on different shapes depending on the environment where they grow.

The name Gypsum comes from the Greek word gypsos, which means plaster and mentions of the minerals are known beginning approximately 300 BC. Around the globe, gypsum forms in massive chunks, clear crystals, and as fibrous bundles. Gypsum is a soft mineral and was chosen as an example mineral by Friedrich Mohs for this Scale of Mineral Hardness.

Physical and Chemical Properties of Gypsum

Gypsum is a soft, evaporite mineral that you can easily scratch with your fingernail. Because of its unique properties, gypsum is great for school projects and in-class experiments. Here are some of gypsum’s interesting physical and chemical properties.

• Chemical Formula: CaSO₄  2H₂O
• Color:   Colorless to white but may appear with shades of pink, tan, yellow, blue, brown, red and gray from the presence of impurities in the mineral.
• Hardness:                 2 on Mohs Hardness Scale.
• Streak:                     White
• Luster:                      Glassy, Silky, Pearly, or Waxy
• Cleavage:                 Perfect
• Fracture:                   Splintery or Conchoidal
• Specific Gravity:       2.312 – 2.322
• Crystal System:        Monoclinic
• Crystal Shape:          Thick tabular to lenticular crystals. At times, maybe prismatic. Varieties can for rosette clusters, granular masses, and fibrous masses.

Varieties and Forms of Gypsum

Gypsum is very common throughout the world and has many varieties that can form as single crystals or clusters of many crystals in varying shapes. Massive Gypsum is a common variety that many people think of when they hear of the mineral.

Gypsum is also known to form “roses” which are clusters of lenticular (lens-shaped) crystals. Alabaster is a fine-grained massive form of the mineral that is typically white in color. Due to its beautiful hue and softness, alabaster is a favorite sculpture medium for artists.

Selenite is a clear, crystal form of gypsum. Clear selenite often has good cleavage planes and a pearly luster. Selenite was named after the Greek word for moon because of the “moonlight” appearance when light reflects off of the crystal surface.

Satin Spar is a white, fibrous form of selenite which forms in long strands, which grouped together, form “sticks.” Satin Spar selenite appears and feels silky.

Uses of Gypsum Minerals

Gypsum is one of the most useful minerals on earth. From ancient times to now, people have found ways to use gypsum in a variety of products including:

• Paint
• Tile
• Drywall
• Blackboard Chalk
• Fertilizer
• Plaster of Paris
• Food
• Hair Products
• Skin Cream
• Environmental Restoration
• Dentistry Impressions
• Sculpture (Blocks of Alabaster)
• Metaphysical practices (selenite variety typically)

9 Gypsum Mineral Fun Facts

1. Gypsum is the most common mineral on earth containing sulfur.
2. Gypsum can form very large crystals, the largest known being 39 feet long found in the Cave of the Crystals in Naica, Chihuahua, Mexico.
3. Gypsum often forms in sedimentary environments like lakes and oceans when the water evaporates leaving the mineral behind.
4. Gypsum will slowly dissolve in cold water.
5. Gypsum has water in its crystal structure. When the mineral is heated, it will lose the water and transform into bassanite (plaster) and then anhydrite.
6. Because Gypsum is very soft and has perfect cleavage, it is very difficult to cut gypsum with facets. This is why gypsum jewelry is not common.
7. White Sands National Monument in New Mexico is made of rare gypsum sand. Gypsum typically dissolves in water rather than breaking down into sand particles, which is why the White Sand National Monument is so special.
8. Gypsum often forms with other minerals like halite (table salt), sulfur, calcite, quartz, pyrite, dolomite, fluorite, and azurite.
9. A sample of gypsum will fluoresce with colors of light blue, yellow and golden yellow under a UV light.

Locations of Gypsum Minerals

Gypsum is found all over the world. Some of the largest and most interesting deposits are located in Mexico, Brazil, Italy, Russia, France, Canada, and the United States.

Explore Gypsum and Add to Your Collection

Mini Me Geology has fabulous samples of gypsum and satin spar selenite available as individual samples and in kits. These great samples are perfect for conducting experiments and adding to a growing collection. Gypsum samples are included in our: My Rockin’ Collection Deluxe Kit, the Junior My Rockin’ Collection Kit, the Colossal Rock and Mineral Kit, Mineral Madness, and the Mineral Observation, Hardness & Streak Testing Kit. If you have any quesitons about gypsum or any of our awesome samples, let us know!

Filed under: Geology / Earth Science on August 28th, 2019