Uric acid stones are not very common. They will not show up on plain xrays but can be detected on CT.
About 85% of kidney stones are calcium oxalate. Under magnification (if any is needed) they look like tiny cockleburrs. First time I saw one I knew why that would hurt! Calcium oxalate is a mineral crystal and it has a LOT of sharp edges. Ouch!
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.