Medium:

100% natural egg shells, the dark eggshell in the center is from the amazing Emu bird...

Eggshell are made almost entirely of calcium carbonate (CaCO3) crystals. It is a semipermeable membrane, which means that air and moisture can pass through its pores. An eggshell is covered with as many as 17,000 tiny pores, the shell also has a thin outermost coating called the bloom or cuticle that keeps the bacteria and dust out. How do eggs get their color you may ask... As the egg moves down the female’s oviduct (the tube that connects the ovary to the outside) it squeezes against glands that produce colored pigments that combine too form every color in the egg shell spectrum. If the egg is stationary at the time that it comes in contact with these glands, it’ll be spotted, If the egg is in motion, it will be streaked.