The stone formed in the human kidney consists mostly of

Kidney stones (renal calculi) form when minerals and salts in urine crystallize and clump together faster than the kidneys can flush them out. Stones are classified by their principal mineral: calcium-based stones (oxalate or phosphate), struvite (magnesium ammonium phosphate, linked to urinary infections), uric acid stones, and cystine stones — and worldwide clinical surveys of stone composition consistently show one type dominates by a wide margin.

Oxalate ions in urine bind readily with calcium ions to form insoluble crystals that aggregate into stones; because of this chemistry, calcium oxalate accounts for roughly 70-80% of all human kidney stones, making it the single most common constituent by far.

• Calcium phosphate stones do occur, but only under more alkaline urine conditions than are typical, which limits how often this composition forms in practice.

• Magnesium-containing renal calculi are associated with ammonium and phosphate (struvite stones, usually tied to urinary-tract infections), not with sulphate — magnesium sulphate is not a recognized stone-forming mineral in the kidney.

• Acetate salts are highly soluble in urine and do not undergo the precipitation/crystallization that forms kidney stones, so calcium acetate is not a recognized stone-forming mineral.

Hence, the stone formed in the human kidney consists mostly of calcium oxalate.