Gypsum
What is Gypsum?
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO₄·2H₂O. It is the most common sulfate mineral. Gypsum is a non-metallic mineral that is typically white, colorless, or gray, but can also be found in various other colors due to impurities. It is known for its softness and can be easily scratched with a fingernail. Gypsum is used in a variety of applications, including the production of plaster of Paris, drywall, and cement. It is also used as a soil amendment and in the manufacturing of various industrial products.
Optical Properties
- Refractive Index
- 1.520-1.530
- Birefringence
- 0.009-0.020
- Pleochroism
- None
- Optical Character
- Biaxial (+)
- Dispersion
- Low
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Gypsum before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Gypsum Localities Map
See where Gypsum is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
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Quick Facts
Physical Properties
- Color
- White, colorless, gray, yellow, red, brown, or black
- Hardness (Mohs)
- 2
- Density
- 2.32 - 2.33 g/cm³
- Streak
- White
Chemical Properties
- Chemical Formula
- CaSO₄·2H₂O
- Elements
- Calcium, Sulfur, Oxygen, Hydrogen
Also Known As
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Gypsum FAQs
How do I identify Gypsum?
Gypsum can be identified by its hardness of 2 on the Mohs scale, White color. Look for these key characteristics when examining specimens.
What color is Gypsum?
Gypsum typically appears in White, colorless, gray, yellow, red, brown, or black. Color can vary depending on impurities and formation conditions.
How hard is Gypsum?
Gypsum has a hardness of 2 on the Mohs scale. This makes it a soft mineral that can be scratched easily.