Thunder Egg : Early Australian Agate Brooch by Stevenson of Adelaide circa 1900

The discovery of agates in a multitude of colours and and formations at “Sinbad’s Valley” in Queensland led to it being a popular Australian gemstone from the 1890’s onwards. This agate brooch with its swirling palette of umber and greys surrounded by a perfect saucer of 15ct gold with a fine rope border detail and a million tiny prongs celebrates the natural variety and uniqueness of agate specimens. Made by the renown Stevenson’s Bros. of Adelaide who were known for their large rage and exquisite quality of jewellery offerings. The Adelaide chapter of the Gemological Institute of Australia has a Stevenson award given to the valedictorian each year, I think that’s pretty cute. Manufacture:  Handmade in 15ct gold, hallmarked to the reverse with the 15ct fineness hallmark and the Stevenson mark for Stevenson’s Brothers of Adelaide. The pin tests as steel. A wide saucer of bloomed gold with a tiny rope border surrounds a large oval shaped agate of umber and grey hues, secured by a million perfect prongs. The brooch fastens with a steel pin with a gold tube hinge and gold c-clasp. A safety chain is attached by a loop on the reverse. The brooch measures 43.5mm x 35.21mm x 6mm (not including the pin or brooch fastenings). Weighs 14.78 grams. Condition:  Very good. The surface of the the face of the agate is smooth and unblemished with no cracking or chips, however there is a chip in the agate on the reverse of the brooch – the chip follows the growth patterns in the agate so it is likely that it has always been missing this little invisible piece. Otherwise in perfect condition.