This is a platinum ring set with a heart cut moissanite. The moissanite measures 5.5mm.
The platinum ring has a beautiful weight to it. The shoulders of the setting sweep up to hold the stone with two round claws at the top and one V shaped claw at the bottom to protect the bottom of the heart and to keep the shape.
Moissanite has a hardness level of 9.25 which puts it between diamond which is 10 and the next hardest gemstone which is sapphire which is 9 making it an ideal gemstone to be worn every day. Moissanite, the world's most brilliant gem, is so called because it sparkles more than diamond and it is both ethical and socially responsible as it grown in a laboratory instead of being mined.
If you want to learn more about how moissanite compares to diamond I have a great blog post that compares them. Is it time to go green when diamond shopping?