These absolutely delicious lab created quartz stones are perfect for all of our precious metal clay jewelers! These stones have a refractive index almost as high as a sapphire which makes for a beautiful play of light that bounces inside of the gemstones. They have a Moh's hardness of 7 which makes them perfect for people who are a little bit harder on their jewelry. These stones can be kiln fired in place up to 1400°