Caliche (Calcium Carbonate Crust)
Calcite-cemented Sedimentary Aggregate · Mineral Specimen / Sedimentary Rock
Crystal System
Trigonal (microcrystalline calcite within an amorphous/massive matrix)
Mineral Group
Carbonates (Aragonite or Calcite group)
Chemical Formula
CaCO3 (with Si, Al, and Fe impurities)
Formation Process
Sedimentary (Secondary precipitation from groundwater evaporation in soil horizons)
About This Crystal
A dense, chalky white to off-white mass with an earthy, dull luster. It appears opaque and powdery on the surface with a rough, irregular texture and visible granular inclusions of sand and silt.
Physical Characteristics
Color: White to light tan; Streak: White; Cleavage: None (massive); Fracture: Uneven/Earthy; Specific Gravity: 2.1-2.5; Fluorescence: Often dull white or orange under UV.
Optical Properties
Opaque; No visible pleochroism or dispersion; typically dull and non-reflective due to microcrystalline structure.
Hardness & Durability
Origin Region
Arid or semi-arid regions globally (e.g., Southwestern USA, North Africa, Australia)
Hardness & Durability
Mohs Hardness: 2.5 to 3.5; High fragility and low toughness; prone to crumbling under pressure.
Care & Maintenance
Keep dry; sensitive to acids (will effervesce and dissolve in vinegar); clean only with soft dry brush; avoid ultrasonic cleaning.
Rarity & Value
Common; Very low monetary value; primarily of geological or agricultural interest rather than gemological.
Special Characteristics
Strong effervescence when exposed to dilute hydrochloric acid; can contain 'ghost' structures of previous organic material or soil grains.
Lore & History
Historically used as a construction material (adobe binder) and in road surfacing. Metaphysically associated with grounding and stability due to its Earth-based formation process.