Agate slab made into a beautiful, one-of-a-kind oil lamp.
Agates are commonly found as nodules that have formed within cavities of volcanic rocks. These cavities are created when gases are trapped within the liquid volcanic material when it hardens. These cavities are then, over time, filled in with silica-rich fluids. Layers are deposited on the walls of the cavity slowly filling it in. Variations in the composition or the conditions of the deposit result in variation in the successive layers as the cavity fills in. These layers include bands of chalcedony, often alternating with layers of crystalline quartz forming the bands that are often associated with agates.