The sphere is the perfect shape. It encloses the most volumn per surface area of any geometric form. Glass is the perfect material. Durable,strong, and harder than steel, infinate in it's possibilities. Opaque, translucent, or transparent and with a vast range of colors. How many reds are there ? How many shades can be achieved by layering a translucent red over different yellows? The possiblities are infinate. A marbles composition of colors and layers presents more varieties.the simplest form is an opaque, translucent, or transparent solid color. Add color to the surface then start layering the interior. Use millifiore techniques to reduce the thickness of canes to a hairs breath. The math looks something like this ; Infinate color possibilities X Infinate composition types = more different marbles than I can make in a lifetime.