They have distinct look from top or bottom, a bit like a wolfs head. They are moderately more spaced than crypts or even eggs. I think they require similar height to silver so only on moderate high mountains or more. If the mountain range is thin, long, and has enough height you should be seeing caves along its length. Its pretty uncommon to not see caves on small mountains that have the height to support them so keep searching. Bigger mountains can have 6+ caves. I think ~3 is the average.

The cave entrance sometimes is easily obstructed from view so if there is a "bulge" type of peak/hill check around it, could be a cave facing weird direction.