Many people can tell sandstone and shale and limestone and even conglomerate, but they're not familiar with chert. Our remote ancestors kept a close lookout for it, because its special qualities made chert a good toolstone. If it was good enough for them, we should add it to our rock repertoire. That's what this new picture gallery of chert is for: to renew acquaintance with this old friend.
Chert beach pebbles Geology Guide photo