How to identify Desert Rose

To correctly identify Desert Rose (Gypsum var. Desert Rose), 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 tan, brown, reddish-brown, or off-white, due to incorporated sand and iron oxides. Can be colorless to white if very pure.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dull to earthy due to sand inclusion; individual gypsum crystals may show a vitreous (glassy) to pearly luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Gritty, sandy, rough to the touch due to embedded sand grains. Can be slightly powdery.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Rosette-like aggregates of tabular crystals, resembling a flower or rose. Individual crystals are often flattened and radiating.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect in one direction {010}, distinct in two others {100}, {011}. However, in Desert Rose, the cleavage is often obscured by the granular nature and sand inclusions.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Arid and semi-arid desert regions, playa lakes, sabkhas, and shallow evaporitic basins where groundwater rich in sulfates evaporates near the surface, often in sandy or silty sediments.

Key Facts

Hardness

2 on the Mohs scale (can be scratched by a fingernail)

Specific Gravity

2.31 - 2.33 g/cm³

Crystal System

Monoclinic

Color

Colorless, white, gray, tan, brown, reddish-brown (due to sand and impurities)

Luster

Vitreous to pearly on crystal faces, dull to earthy on sandy surfaces

Transparency

Transparent to translucent to opaque (depending on sand content)

Fracture

Uneven to conchoidal (rarely observed due to crystal habit)

Cleavage

Perfect in one direction {010}, distinct in two others {100}, {011}

Composition

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

Physical characteristics

• Crystal Habit: Rosette-like aggregates of tabular crystals, often radiating and intergrown with sand grains.
• Cleavage Type: Perfect basal cleavage {010}, allowing thin sheets to be peeled; distinct prismatic {100} and pyramidal {011} cleavages.
• Fracture Type: Uneven to conchoidal, but rarely observed due to the aggregate nature.
• Tenacity: Sectile (can be cut with a knife), flexible in thin sheets (selenite variety), but brittle in Desert Rose form due to sand inclusions.
• Luster Type: Vitreous (glassy) to pearly on crystal surfaces; dull to earthy on sandy surfaces.

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