4.3" Polished Banded Agate with Wegeler Effect - Aouli, Morocco

The wegeler effect, also known as the shadow effect or parallax effect, is a three-dimensional oddity in which rotating the agate results in the appearance of lines that move. One line will move with the source of light while the other moves with your point of view. This occurs in agate that has tightly packed, alternating bright opaque bands and transparent bands.

Agate is a variety of microcrystalline quartz (chalcedony) that displays translucence and in some cases banding. Agate primarily forms when silica-rich fluids fill pockets within rock and/or fossils, resulting in deposition of the silica along the walls of the rock. This process can result in banding patterns as the composition and impurities of the fluids change over time. These banding patterns can either form as flat layers or rounded layers, depending on the surfaces available for deposition.