8.7" Graveyard Plume Agate Slab - Eastern Oregon

Long known for its beautiful "plume" inclusions that look like moss or snow-covered trees, agate from this area comes from just a couple of small mines. Plumes or dendrites that occur within rock are most often a result of intruding (percolating) mineral solutions that contained manganese and/or iron. These solutions can work their way through microscopic cracks in the rock, leaving behind a branching pattern throughout the agate. To an untrained eye, these can be mistaken for plant fossils within the rock.

About Agate

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 rocks and/or fossils, depositing the silica along the walls of the rock. This process can result in banding patterns, as the compositions and impurities of these depositing fluids change over time. These banding patterns can either form as flat layers, creating linear patterns known as waterline agate, or as rounded layers, forming more common ring-like patterns. These patterns depend on the surfaces available for deposition.