It is actually not an excess of calcium that's usually the problem, calcium deficiency is actually a greater risk for most. While yes, the most common types are both chemicals that are in part calcium, the body is meant to produce them, just in different parts of the body. Usually, a deficiency in calcium allows those other compounds that should be used up in other places to be flushed through the kidneys, possibly building up. Then incidental calcium that does move through the kidney binds to them there. Higher dietary calcium intake is associated with a sharp decline in stone risk, though extremely high intakes from vitamin supplements etc do increase risk. But in general, it is an excess of the things that bind to calcium that are the things to avoid, apparently almonds are pretty much the worse thing ever, with a fairly distant second being chocolate.