4.7" Polished Banded Laguna Agate Slab - Mexico

Laguna agate is a highly sought after variety of banded chalcedony. It often forms in bands of red, pink, white and/or scarlet hues, with some specimens containing bands of brown and golden yellow chalcedony. The first documented finds of this agate occurred in the late 1940's and since then have been extracted from several sites near Ojo Laguna, Chihuahua, Mexico. These agates are believed to be roughly 38 million years old.

Like many other agates, Laguna agates form by deposition of microscopic silica crystals in concentric layers within cavities of rocks. The colors of the agate are dependent on impurities within the silica-rich solutions, of which are often supplied by the surrounding rock.

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.