Gypsum
Mineral CaSO4·2H2O
Take care.
- Fragile: Handle it gently and pack it well; it breaks or crumbles easily.
- Damaged by water: Keep it dry: don't wash it, and keep it out of damp places.
About it
Soft enough to scratch with a fingernail, with a pearly cleavage that peels into bendable flakes. Grows as clear selenite blades, silky satin spar, and sandy desert roses; giant crystals fill the Naica caves in Mexico.
- Type
- Mineral
- Group
- Sulfate, gypsum group
- Formula
- CaSO4·2H2O
- Hardness (Mohs)
- 2
- Specific gravity
- 2.31–2.33
- Streak
- white
- Lustre
- vitreous (glassy), pearly, silky
- Crystal system
- Monoclinic
- Colours
- colourless, white, grey, tan, yellowish, pink
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect in one direction, flexible but not elastic flakes
- Under UV light
- some glow white, blue, or greenish under UV
Typical values: real specimens vary. For more, see mindat.org.