Diamond proportions and facet names, for the round brilliant cut. Figures 1 and 2 of [1] .  Edited to omit brand names and other context. Copyright 2001 by Jasper Paulsen.

Licensing
Marcel Tolkowsky's 1919 edition of Diamond Design is in the public domain in the United States, because it was originally published simultaneously in London and New York.
This image is derived from http://commons.wikimedia.org/wiki/Image:Diamond facets.gif, which is copyright 2001-2005 by Jasper Paulsen.  Diamond facets.gif is licensed under the GNU Free Documentation License; that is the license under which this derivitive work (Diamond_facets.svg) was made.
The uploader of the svg file (User:Danuthaiduc) placed the derivation of the svg file from the gif file into the Public Domain, using the PD-self template.  Note that User:Danuthaiduc was not authorized, and is not authorized, to place either the gif file or the svg file into the public domain.

Therefore, this image is licensed under the GNU Free Documentation License:
Diamond_facets.svg
Diamond_facets.svg: User:Danuthaiduc
derivative work: Rolf Obermaier (talk)