Finished tilling up a new field for planting, and spent most of the time clearing all kinds of rocks from the place. Looked like someone had just poured them out, right below the topsoil.
Couple of the farmhands were slacking off and throwing the rocks around... and damned if one didn't break open and have some kind of crystals inside! Don't know what they are, but they're pretty. Might fetch a good price the next time we go in to market.