All are true about pigemented stones except

Pigmentes stones Black stones Black stones are composed of insoluble bilirubin pigment polymer mixed with calcium phosphate and calcium bicarbonate Predisposing factors Hemolytic disorders (Heriditary spherocytosis, sickle cell anemia) Mechanical prosthetic hea valves Cirrhosis Gilbe's syndrome Cystic fibrosis Ileal disease or resection Brown stones Brown pigment stones contain calcium bilirubinate, calcium palmitate and calcium stearate as well as cholesterol Typically found in Asia Rare in GB Formed in bile duct Related to bile stasis and infection Gram negative bacteria (E.coli and Klebsiella) secretes beta-glucuronidase, which deconjugate soluble conjugated bilirubin Free unconjugated bilirubin precipitates and combines with calcium and bile to form brown pigment stones Stones form whenever static foreign bodies are present in the bile duct (stents or parasites such clonorchis sinensis and Ascaris lumbricoides) Ref: schwaz's principle of surgery 10th edition Pg no : 1491