Collection: Gypsum

Gypsum is a common mineral composed of hydrated calcium sulfate , with the chemical formula CaSO₄·2H₂O . It is a soft mineral (hardness 2 on the Mohs scale), often white or transparent, but it can also have gray, pink, or yellowish hues depending on the impurities it contains.

Main features:

• Composition : Calcium sulfate dihydrate

• Hardness : 2 (it can be scratched with a fingernail)

• Cleavage : Perfect

• Density : Approx. 2.3 g/cm³

• Appearance : Tabular crystals, fibrous masses, or granular forms

Common forms:

• Selenite : Transparent gypsum, in well-formed crystals

• Alabaster : Solid white gypsum, used in sculpture

• Fibrous gypsum : Sometimes called "spaghetti stone" or "angel hair"

• Sand roses : Rosette formations found in desert regions

Origin :

Gypsum is formed primarily by evaporation of water in shallow marine environments or salt lakes. It is an evaporite mineral . It is often associated with sedimentary rocks.

Uses:

• Plaster industry : When gypsum is heated to about 150°C, it loses water to become plaster of Paris (CaSO₄·½H₂O). Adding water produces a paste that hardens.

• Construction : Plasterboard partitions ( plasterboard type, BA13 , etc.)

• Agriculture : Improving acidic or compacted soils

• Sculpture and crafts : Especially alabaster

• Medical : Formerly used for casts and bandages

Interesting facts:

• Gypsum is one of the first minerals used by man in construction, since Antiquity (Egypt, Mesopotamia).

• It is an indicator of the evaporation of ancient aqueous environments in geology.

• It is often found in very large deposits , notably in France (Montmartre in the past), Morocco, Canada, or the United States.