2.5" Polished Botswana Agate Nodule - Botswana, Africa
This is a beautiful 2.5" wide banded agate nodule that has been polished to a mirror finish on one side. These agate nodules are collected from the Bobonong District of Botswana, Africa. These agates feature gorgeous parallel banding in a variety of color hues including white, blue, grey, purple, pink and red. This specimen exhibits the wegeler effect.
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.