Minerals

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General Information

Desert Rose

Gypsum is made of calcium sulfate and can be found in 4 different variants: desert rose, selenite, gypsum flower and alabaster.

Desert rose is a combination of mineral gypsum and sandgrains. The sandgrains are integrated into the crystal structure of gypsum (some times baryte). Desert rose cannot be classified as a mineral or stone, although the latter is mostly the case. Desert rose is formed when water with gypsum or baryte dissolved in it, evaporates (mainly in desert areas). The sandgrains that are present will stick on the plane around the c-axis of the crystal.

Selenite usually forms thin crystals and gets its colour from contaminations like other minerals.[1]

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Chemical & Physical Information

Trivial NameGypsum
Chemical NameCalcium Sulfate Dihydrate
Chemical FormulaCaSO4,2H2O
Density2,3 g·cm-3
Molar mass172.17 g·mol-1
Hardness2
Crytal systemMonoclinic
Unit cell?
Crystal habitSandy dull, clay like structure
FractureFibers
CleavagePerfect [010], vague [100] and [110]
ColourColourless, white, brown, green or combinations.
LusterPearl
StreakWhite
OpacityTransparent to translucent.
SafetySafe
ExtraAbundant with many applications.
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Photos

Desert Rose

(2 cm)

Desert Rose

(1 cm)

Selenite

(8 cm)

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Sources

[1] Wikipedia (Gypsum)

[2] Wikipedia (Desert Rose)

[3] Specimen from my personal collection, photo taken by me.