Hot Beginnings… Mt Hay’s thundereggs formed in silica-rich volcanic rocks resulting from ancient lava flow called Rhyolite 120 million years ago.
Trapped in Time… The flowing Rhyolite trapped small particles and tiny gas bubbles, leading to the development of ‘volcanic birthstones’.
Formation… Thundereggs occurred when two forms of crystallization took place creating spherulites and spheruloids. Spherulites are a radical growth created when minerals crystallize around a nucleus. Spheruloids are a hollow form created when minerals crystallize around a steam bubble.
Stars in the Stone… As the lava cooled the star shaped cavity often seen in thundereggs (spheruloids) developed.
Lasting Layers… The cooling caused minute cracks to occur, allowing silica-rich solutions to seep into the cavities. This filled them with minerals such as quartz, agate, chalcedony, quartz crystals, amethyst, jasper and opalite.
There is a Caravan Park at Mt Hay.
You drive up a steep rocky road to the very top and there is a shop, a gemstone Workshop and also a Pewter Workshop, as well as a fossicking area. Tourists are given a hand pick, a bucket of water and a brush for washing the stones, and a plastic bag for collecting them for the price of $20.
Here the thunder eggs and cut in two, polished and prepared for retail.
Fossicking as well as a mine tour costs $30 and 2 stones are also cut in this price.
It is a very beautiful and tranquil location set in the mountain and there are powered sites and cabins for accommodation. I intend to return and stay a few days.
The stones you see in the first photo are what I collected and had cut.
Contact Mt Hay Gem Tourist Park for more information about tours and fossicking (Phone: 07 4934 7183).