Thunderegg Slab #380 - Agate Creek Queensland (stand not included)
approx. size 14.5cm width x 11cm height x 2cm depth
455 grams
Thunderegg helps to build self confidence and self-esteem. Thunderegg enhances mental functions, improves concentration, perception and analytical abilities. In ancient mythology, it was believed that Thundereggs were thrown down to the earth by angry gods when displeased by human events.
Agate Creek, south of Forsayth, is world-renowned for agates of superb colours and patterns.
The fossicking localities occur in the basin-shaped area of Agate Pocket, which is underlain by rocks of the Agate Creek Volcanic Group, a remnant of a volcanic sequence of early Permian age. This was deposited on a basement of granitic rocks of the Robin Hood Granodiorite. Three formations are recognised: the Big Surprise Tuff, Black Soil Andesite and Thunder Egg Rhyolite. Intrusive bodies of much the same age have penetrated the volcanics, including rhyolite and the Connie May Dolerite. In later Jurassic times, the volcanics were covered by sandstones and conglomerates of the Hampstead Sandstone; these have since been stripped off and now remain only as hill cappings on the south-western escarpment bordering the pocket and at the head of Spring and Agate creeks.
Agate occurs as amygdales (filled gas bubbles) in the upper parts of basaltic andesite lava flows (Black Soil Andesite) and thunder eggs occur as spherulites in rhyolitic lava (Thunder Egg Rhyolite) which forms the north-eastern rim of the pocket.
Agates occur as nodules (solid agate) or as geodes, roughly ellipsoidal or rounded in shape in various sizes but averaging about 50mm. The agate is often multi-coloured and usually banded in straight, curved or irregular patterns. The thunder eggs in the rhyolite may contain infillings of red-brown jasper.
Black Soil Creek, Crystal Hill, Bald Hill, Simpsons, Blue Hills and Flanagans are the main areas of interest. Agates can be separated from the decomposed lavas by hand digging.
Because the agate is hard and resists weathering, searching down-slope colluvial deposits may also be productive as agates are released and transported from the host lavas. The alluvium of black soil and gravel of present day drainages is also worth attention, especially after the wet season.