Objects used for scrying are reflective, translucent, or luminescent. Ancient Greeks used the reflections in pools of water. Nostradamus used black obsidian bowls with water. The most common are ANY reflective black objects such as plastic, glass, water, or black semi-precious gemstones like black obsidian. The scrying medium doesn't matter as much as your ability to stare at an object and achieve a trance state. Scrying means to perceive or reveal.