4" Polished Cold Mountain Thunderegg (Half) - Mexico

This is a beautiful, polished Cold Mountain Thunderegg specimen collected from the Sierra Mountains of Mexico. The autumnal colors of this specimen are stunning and contrast nicely with the pockets that show clear water line deposition. This nodule half would make a wonderful addition to any agate collection. The face of this specimen has been polished to a glossy finish and the back half is still in its raw form.

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.

Chalcedony var. Agate
Sierra Mountains, Mexico
4 x 3.1"