Is there another way to get more elemental stones?
Go into caves, and when you see those swirly dust clouds walk into those they can give you stones, elemental gems, or fights with Drilbur/Excadrill.
Go in a cave and a Drilbur/Excadrill may Dig one up for you in a cloud of swirling dust. You can buy them in Black City in Black.
a) black city
b) dust clouds in caves.
pardon me for the short answer, i am to the point and in a rush.