Western opal fields
Yowah fossicking area
The Yowah opal field, which includes the nearby area known as Black Gate, is the southernmost opal mining centre of western Queensland; it is popular with tourists and fossickers as it has easy access from main roads and has shops, fuel, telephone, a caravan park and permanent bore water supply. A small local population increases significantly during the winter season.
Yowah is about 160km west of Cunnamulla. Travelling towards Thargomindah, turn off to the right about 18km west of Eulo onto the Yowah/Toompine road and travel 48km via Alroy homestead to the Yowah–Quilpie turn-off. Continue a further 23km to Yowah; this last 23 km is unsealed.
From Quilpie, drive 110km through Toompine to the Eulo/Yowah turn-off. Turn left and follow this mainly unsealed road for about 56km to the Yowah turn-off, and then continue the further 23km as above.
Camping is prohibited. There is accommodation available in the town of Yowah.
A feature of the Yowah field is the occurrence of precious opal in siliceous ironstone nodules generally referred to as Yowah Nuts. These nuts range from about 5mm to 200mm across, have a spherical or ellipsoidal shape, and show alternate concentric rings or bands of light- and dark-brown siliceous ironstone. There is sometimes a kernel of precious opal, which is the main source of the gem.
The nuts are found in layers (150–600mm in thickness) at depths up to 20m in a ferruginous sandstone, and are commonly associated with mudstone fragments or clay pellets.
The main layer is located near the contact between the sandstone and underlying mudstone/claystone, but scattered nodules, and in some cases a second band, may occur above.
The lateral continuity of the nut bands is somewhat difficult to predict owing to the irregular bedding of the strata, as well as the lack of any detailed mapping. In some shafts, the nut band was not encountered, but the sandstone at its contact with the mudstone was found to be more ferruginous and cemented by partial opalisation into a hard band, which also contained opal in the form of seams and pipes.
The eastern part of the fossicking area has always been popular with tourists as a place to speck or noodle fragments of opal or ironstone matrix from the surface or shallow depth. In this area the main nut band appears to have been exposed at the surface, so that a layer of loose rubble of broken ironstone nut fragments covers the surface to a depth of about 600mm. Spotting chips of opal or fragments of matrix while digging through this material is relatively easy with a bit of practice.
Several mining claims and mining leases are currently within the fossicking area and are shown on the Yowah fossicking map (PDF, 374KB); these must not be entered without the permission of the holders.
In this guide: