Knock these rocks together for an electrical effect. Flash rocks are one of the few minerals with piezoelectric properties. So, when subjected to mechanical stress, these two little rocks generate an electrical charge and glow.
Just place a rock in each hand, and forcefully rub the rocks together. To see the glowing electrical effect fully, you should do this in a darkened room. Also, note the distinctive odor given off by the frictions.
Made in the USA. Stone size varies. Card measures 3.5 inches wide x 6 inches long.