Persian cat since the early 1990s and the Persian lost its top spot to the British Shorthair in 2001. As of 2012, it was the 6th most popular breed, behind the British Shorthair, Ragdoll, Siamese, Maine Coon and Burmese. In France, the Persian is the only breed whose registration declined between 2003 and 2007, dropping by more than a quarter. The most color popular varieties according to CFA registration data are seal point, blue point, flame point and tortie point Himalayan, followed by black-white, shaded silvers and calico. The breed standards of various cat fancier organizations may treat the Himalayan and Exotic
Crystallographic point group known as a crystal class. There are infinitely many three-dimensional point groups. However, the crystallographic restriction of the infinite families of general point groups results in there being only 32 crystallographic point groups. These 32 point groups are one-and-the same as the 32 types of morphological (external) crystalline symmetries derived in 1830 by Johann Friedrich Christian Hessel from a consideration of observed crystal forms. The point group of a crystal, among other things, determines directional variation of the physical properties that arise from its structure, including optical properties such as whether it is birefringent, or whether it shows the Pockels