Rainbow Moonstone Cut Tube 5x7mm. Moonstone is an alternate birthstone of the month of June, alternate to Pearl. Moonstone is believed to bring good fortune and help foretell the future. Its name is derived from its floating light effect and sheen which is compared to the light of the moon. Moonstone usually come in white, colorless to light grayish blue. Sometimes you will see a little of yellow, brown, orange, blue or green.