Natural Gemstone Beads Stretch Rings, Faceted, Round, Size: about 18mm inner diameter, beads: 3.5x3.5mm. âPlease Note: These beads may include Natural Amethyst, Tourmaline, Rose Quartz, Amazonite, Tanzanite and so on(as the picture shows). but as it is a mixed product, the stone type is delivered randomly, please refer to the actual product delivered.