They’re not very common but to give people suggestions that they should change their diet without analyzing the stone is crazy.
There are two clinics that analyze stones. One is at Mass General. It’s been there for decades. You need to know what kind of stone you have.
85% of stones are calcium oxalate. If you already have gout consider uric acid stones. If they can be seen on plain xrays or fluoroscopy they are calcium oxalate. Recovered stones are usually sent for analysis if the patient wants to do it (and pay for it).