Now I know why two gems and at least on bug (moonstone and bloodstone and the light beetle) have shown up in my yard. I did the buydebug to see if there were any spawners and yep, there they were. I had put out some spawners of butterflies and one lizard, you can't have flowers without butterflies or rock without lizards, so they are for looks, not usage. But now I don't feel bad about the gems and bug in my yard that I didn't put out.
When my sim was doing some alchemy, it stated something about how she was ready for mixing drinks, not sure what that meant.