Thunder Egg Agate (02)
This listing is for the exact specimen pictured.
WHAT IS IT
A thunder egg is a nodule-like rock, similar to a filled geode, that is formed within rhyolitic volcanic ash layers.Thunder eggs are rough spheres, most about the size of a baseball—though they can range from a little more than a centimeter to over a meter across. They usually contain centers of chalcedony which may have been fractured followed by deposition of agate, jasper or opal, either uniquely or in combination.
Agates are rocks consisting of microcrystalline quartz called chalcedony. They are typically formed in pockets within cooled lava. As water flows though the lava, the pores in the cavities— called vesicles—act as tiny filters which catch silica particles that were in the water. As these particles accumulate, various silica- based minerals can be deposited to create colorful bands in the rock which can be seen whenever the rock is cut open.