Pink Tourmaline Birthstone Diamond Ring 10K White Gold10k white gold diamond and pink tourmaline birthstone ring. The perfect October birthstone ring or mothers ring, this 10 karat white gold band has round pink tourmalines and diamonds alternating half way around the ring. All birthstone rings and mother's rings are available in all birthstones, although the April (diamond) version may cost more. Looks great worn alone, or as a stackable ring.