I think your marble site is wonderful. I am so pleased to be able to find real rock crystal marbles. I use them in jewelry making. Finding 1/2" to 3/4" undrilled rock crystal beads has been nearly impossible. I'm glad I finally found a source.
Size is as-packaged, or the diameter of loose marbles. ("D" is the diameter of round items other than marbles.)
These golden "brassies" are as devastating as steelies. Both are very dense and will send opponent's marbles flying, but brassies have a beautiful golden luster, and so they are especially prized. They are also corrosion-resistant, and won't rust like steelies.