There are different types of kidney stones. The calcium ones are most common. They can analyze them and tell you what kind you have.
Uric acid type stones require a different diet that avoids purines.
Go see a doctor before the stone obstructs or cuts you inside and it gets infected.
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!