Moissanite is a lab created, synthetic gem that is the closest to looking like a diamond as you can get! The moissanite is more durable, and will take more wear than a cz. It's brilliance is like that of a diamonds, at about an 1/8 of the cost.
This one is 1.1 carats, measuring at 7mm. There are many others to choose from.
Some opt to put his in a semi mount with genuine diamonds, but it can also stand on it's own in a basic mounting!