mineral

Kidney Stone

Calcium Oxalate (CaC2O4·nH2O)

Hardness: 2.5-3.0 (Mohs). Color: Tan, brown, or grey. Luster: Dull to waxy. Crystal structure: Monoclinic (Whewellite) or Tetragonal (Weddellite). Surface: Rough, jagged, or crystalline.

Hardness: 2
Color: Tan, brown, or grey
Luster: Dull to waxy

Identified May 26, 2026More mineral →

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Physical properties

Hardness: 2.5-3.0 (Mohs). Color: Tan, brown, or grey. Luster: Dull to waxy. Crystal structure: Monoclinic (Whewellite) or Tetragonal (Weddellite). Surface: Rough, jagged, or crystalline.

Formation & geological history

Formed within the human urinary tract when minerals and acid salts become concentrated and crystallize out of urine. This biological mineralization process is known as nephrolithiasis.

Uses & applications

Medical diagnostic value. These specimens are typically analyzed by doctors and laboratories to determine dietary or metabolic causes of stone formation.

Geological facts

The most common type of kidney stone is calcium oxalate. Despite being biological in origin, they are composed of minerals that also occur naturally in geological settings, though the specific biological conditions of formation are unique.

Field identification & locations

Identified by their passed or surgically removed status through the urinary tract. Collectors are rare as these are medical specimens, but they are often kept by patients as personal mementos of a painful event.