My mother has developed bladder stone. what is it exactly?

Precipitated salts: Urinary stones form when various salts normally excreted in urine crystallize and grow into stones. In some cases it may be due to metabolic disorders causing increased calcium excretion, high uric acid or cysteine. Bladder stones can cause pain, bleeding, urinary obstruction and infections.

Stone in bladder: Bladder stones are typically found in people who have difficulty emptying the bladder (retention of urine) and chronic urinary tract infections. Can also be found in those with bladder abnormalities such as diverticulum. Bladder stones are generally treated with an endoscopic procedure using a laser to fragment the stone. Occasionally, if stone is large, it may be removed with abdominal surgery.