How to identify Desert Rose

To correctly identify Desert Rose (Gypsum (Selenite variety)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically sandy brown, tan, reddish-brown, or off-white, depending on the color of the incorporated sand and other impurities. Pure gypsum roses can be white or colorless.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to earthy due to the sand content; individual gypsum crystals within the aggregate may exhibit a vitreous (glassy) to pearly luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Rough, gritty, and sandy to the touch due to the embedded sand grains. The crystal 'petals' can feel smooth if not heavily encrusted.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Rosette-like aggregates of tabular or platy crystals radiating outwards, resembling a flower or rose. Individual crystals are monoclinic.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Gypsum has perfect cleavage in one direction {010}, good in another {100}, and distinct in a third {011}. This can be observed on individual crystal faces within the aggregate, but is often obscured by sand.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Arid and semi-arid desert environments, playa lakes, sabkhas, and shallow evaporitic basins where groundwater rich in sulfates evaporates near the surface.

Key Facts

Hardness

1.5 to 2 on the Mohs scale (for gypsum, the sand content can make it feel slightly harder but the gypsum itself is soft)

Specific Gravity

2.31-2.33 g/cm³ (for gypsum; the sand content will slightly increase this value)

Crystal System

Monoclinic

Color

Variable, typically sandy brown, tan, reddish-brown, or off-white

Luster

Dull to earthy (aggregate), vitreous to pearly (individual crystals)

Transparency

Opaque to translucent (aggregate), transparent to translucent (individual crystals)

Fracture

Uneven to conchoidal (for individual gypsum crystals, but often obscured by aggregate nature)

Cleavage

Perfect in one direction {010}, good in another {100}, distinct in a third {011}

Composition

Hydrous calcium sulfate (CaSO4·2H2O) with significant sand (silica) inclusions

Physical characteristics

• Crystal Habit: Rosette-like aggregates of tabular or platy crystals, often heavily encrusted with sand.
• Cleavage Type: Perfect basal cleavage {010}, good prismatic {100}, distinct pinacoidal {011}.
• Fracture Type: Uneven to conchoidal (for pure gypsum, but often appears irregular due to sand).
• Tenacity: Sectile (can be cut with a knife), flexible in thin sheets (for pure selenite), but the aggregate is brittle.
• Luster Type: Dull to earthy (due to sand), vitreous to pearly (on exposed gypsum crystal surfaces).

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