Round Colorless Moissanite Center Stone 6.5mm6. 5mm Round Colorless Moissanite Center Stone. This stunning alternative to a traditional diamond creates tremendous sparkle at a fraction of the cost. Measuring at 6. 5mm in diameter, this moissanite center stone is the same size as a traditional 1ct round diamond. Moissanite is known for its hardness (similar to sapphire), and exceptional fire. These stones generate lots of colored light, due to being doubly refractive. All moissanite are