What is the cause of the Doubling of back facets of Pavillion in Zircon?
Natural Zircon is doubly refractive. This means that a ray of light passing through this sort of gem is slowed, bent and split in two as it passes through the medium. Sapphire, Peridot, Tourmaline and Synthetic Moissanite are also doubly refractive stones.
The effect of double refraction becomes visible, for example in Zircon or Peridot, when the back facets of the stone are viewed through the table. There seem to be two of every facet and the culet. This effect is called doubling.
