Ammonium biurate crystals are normal in urine. Appearance: yellowish-brown, can be seen in a "thorn apple" shape . However, the presence of ammonium biurate crystals especially in combination with a urine pH 9.0 or higher usually indicates an old or poorly preserved specimen. Best practice is to NOT report any urinalysis results on the sample as it has been compromised. A recollect should be requested.