Large Thunder Egg | Half

From Central Queensland, Australia, weight 445g | 10x9x4cm approx.

Formed at the birth of Mt Hay near Rockhampton, Queensland, 120 million years ago, visitors from around the world are amazed by these volcanic gas bubbles.

As molten lava cooled, a rhyolite shell formed around trapped gas bubbles. This shell cracked allowing the gases to escape, leaving behind a hollow cavity. Siliceous liquids containing minerals and impurities entered the cavity and crystallized, sealing the cracks and forming the mysterious centres. These colourful centres are usually made up of agate, chalcedony, jasper, quartz crystal or a combination of these minerals.