What are kidney stones made of?
Approximately 80% of kidney stones are predominantly calcium salts.
Calcium oxalate is the major component in 85% to 90% of calcium stones, the rest being calcium phosphate, in the form of apatite or brushite.
It is common for small amounts of apatite to be found in calcium oxalate stones. About 10% of stones are uric acid and 5% to 10% are struvite (magnesium ammonium phosphate).
Cystine accounts for about 1% of all stones. Stones may be a single pure substance or may be a mix of crystal types, such as calcium oxalate and uric acid.
