[Kidney Stone type] Calcium oxalate [Population] 80% [Color] Black/Dark brown [Sensitivity] Radio-opaque [Details] Some of the oxalate in urine is produced by the body. Calcium and oxalate in the diet play a part but are not the only factors that affect the formation of calcium oxalate stones. Dietary oxalate is an organic molecule found in many vegetables, fruits, and nuts. Calcium from bone may also play a role in kidney stone formation. [Circumstances] 
when urine is acidic (decreased pH)[48]