Calcium oxalate stones result from the crystallization of oxalates in the kidneys. Oxalates can come from diet or metabolism. Some people absorb more oxalates. Some people have low urinary citrate so oxalates can crystallize easier. Take a look at my ebook:

https://www.amazon.com/Calcium-Oxalate-Kidney-Everyone-Medicine-ebook/dp/B087F9LCM4