“...Tyalgum Creek is a tributary of the Oxley River which is part of the Tweed River system. This river system is located in the far north of New South Wales, Australia near the Queensland border and enters into the Pacific Ocean.
The agate here is found mainly in the creek gravels having been washed down from the higher mountain ranges which formed part of the rim of the Mt Warning shield volcano.
Most of the agate from this creek is clear to light grey/blue. There is a lot of water level banding in the material found in the creek gravels. The size of the agate material ranges from golf ball size up to large (3 to 4 kg ) nodules.
Associated with the agate is also, chalcedony, thunder-eggs, green jasper and rhyolite. The best time to collect in this area is after floods when the gravel beds have been extensively churned over. Most of the floods occur in the summer months, December to April...”
pers. report from John Nedwich