❇️ Different Types of Kidney Stones Kidney stones (renal calculi) are hard mineral and salt deposits that form inside the kidneys when urine becomes concentrated. There are several types of kidney stones, each with different causes, risk factors, and prevention strategies. 1. Calcium Stones Calcium stones are the most common type, accounting for about 70–80% of cases. They are usually made of calcium oxalate, and less commonly calcium phosphate. Risk factors include dehydration, high oxalate int