Two of these pieces are described in great detail, and as I was going through the edits, I realized that there was something interesting about them. Each is set with a large stone, and one is faceted, while the other holds a cabochon. And making sure that the correct cut is in each piece was more than just a whim -- it adds yet another dimension to the story.
One of the pieces is known in legends as the Sunstone. It is a heavy golden pendant in the likeness of a gryphon carrying a large topaz-like stone on its back. In this case, with a fairly transparent stone, a faceted cut is most logical. The reason that transparent or translucent stones are usually faceted is to enhance their reflective properties. The facets are what gives these gems their "sparkle." Facets also tend to be cut in the harder stones, like diamonds, emeralds, rubies, and topazes because they do not scratch as easy as the opaque gems tend to do.
The second key piece is known as the Moonstone. It is a scribed silver disk depicting a half-moon with a moonstone held between the horns of the crescent to complete the circle. The stone in this case is cut into a cabochon. This cut is generally a flat base with a domed, polished top. It is often oval in shape because it is easier to fool the eye to slight imperfections than to shape a completely round circle in stone. Cabochon cuts are usually used in the opaque, softer gems, because the polished finish helps hide scratches in the more easily damaged rock. Opals, amber, and tiger eye are stones that are often seen as cabochons.
In the book, there are definite correlations between the brilliant, refracted light of the sun and its representation by the faceted Sunstone, and the cool, polished glow of the moon encapsulated in the Moonstone. Using the correct cut in each is just one more way to point up the differences and throw in a bit of authenticity. The devil is in the details.
For more information on Cabochons, here is an interesting website showing how they are made: http://www.rockhounds.com/rockshop/oplc_cab.shtml
To learn more about faceted stones, here is a how-to for creating one: http://www.gemsociety.org/info/gemlore/gl_02.html