The Legacy of Bert Kayes

By Patrick O'Brien

This story begins 120 million years ago, give or take a million years, when horrible big beasties roamed the planet and the night sky was lit by a multitude of erupting volcanoes. At that time, 40km west of Rockhampton, which, I imagine, was then only a very small village, one such volcano roared into life spewing hot stuff everywhere and for reasons I know not, they called it Mt Hay.

From the evidence seen today, the initial eruptive phase produced pyroclastic rocks followed by rhyolite lavas and lastly, in its final phase, it ejected more pyroclastic material. This whole seething, bubbling mess eventually began to cool, trapping squillions of gas bubbles in the hardening lava. These bubbles in turn cracked in the heat and pressure, allowing the gas to escape leaving cavities which eventually filled with silicas such as agate, chalcedony or jasper. Some cavities however were taken over by crystalline minerals and filled with amethyst, citrine, smoky quartz and so on.

These now filled gas bubbles became round rocks known as spherulites and spheruloids. The spherulites were just that, a solid rock, however the spheruloids contained the wonderfully attractive crystal and agate gel material we prize so much and call ‘thunder-eggs.

Reputedly, these thunder-eggs were so named because as the lava degraded into rich farming soil and was duly spread around the countryside by heavy rains and floods, the thunder-eggs became exposed and early man (or woman) believed that they had fallen from the sky during storms and were the eggs of the gods of thunder.

You must admit that while early man was technically incorrect, back then their version of the eggs’ creation would have sounded more believable than the scientific one!

The full article can be found in the May 2010 issue of Gold Gem and Treasure. Subscribe now.

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