Agate Creek, south of Forsayth, is world-renowned for agates of superb colours and patterns.
The fossicking area is about 70km south of Forsayth by a gravel road, which is suitable for conventional vehicles, but may be impassable in the wet season (see map). From the township, head south-west towards Gilberton and at 11km turn right for a further 15km to the North Head turn-off. Turn left and continue south to the Robertson River. The crossing is about 100m wide in soft sand. The Cave Creek crossing also requires care. After passing the entrance sign to the fossicking area, turn left after crossing Agate Creek.
Camping is not permitted in the fossicking area but the landholder, David Terry, allows camping nearby, adjacent to Agate Creek outside the fossicking area. Camping is not permitted elsewhere on Robin Hood station or adjoining properties. A range of accommodation options is available in Forsayth.
The creeks in the area are usually dry but water may be found in Black Rock Waterhole and Banyan Spring.
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 recognized: 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 (see map). 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.
Two mining claims (MC 30027 and MC 30028) within the area are excluded from the declared fossicking area (see map); these must not be entered without the permission of the holders. Miners Homestead Lease MH 1551 is also excluded from the fossicking area.