18-karat white gold. Amethyst gemstone = 5.00 ct. Put (the right) Ring on It: Size Guide. Ring can be re-sized by any professional jeweler; however if re-sized it will not be accepted for return. It is customary to treat most gemstones to achieve enhanced colour and durability. Some of these treatments may not be permanent and may require special care. Accompanied with manufacturer's packaging. Our products are 100% genuine. In some cases we purchase merchandise from trusted independent suppliers and not directly from the brand owner. In all cases we stand by the authenticity of every product sold on our site.