Northern Queensland fossicking
O'Briens Creek fossicking area
O’Briens Creek near Mount Surprise is well-known for gem-quality topaz, attracting visitors from all over Australia and overseas.
Mount Surprise is a small township about 200km south-west of Cairns between Mount Garnet and Georgetown on the Gulf Developmental Road. From the township go north-west across the rail line on the Mount Surprise Station road and travel 37km to cross Elizabeth Creek. Follow the sign to the fossicking area along the road to the left for a further 1.5km, passing Diggers Rest about 200m before the main entrance sign. Refer to the map for details of tracks and signs within the fossicking area and note boundary limits.
The gravel road to O’Briens Creek may become impassable in wet weather and care is required on black soil sections. Flooding of creeks and gullies occurs during the wet season. Check local conditions before setting out.
Camping is not permitted in the fossicking area. However, the landholder of Mount Surprise Station allows camping nearby, at a site adjacent to Elizabeth Creek with basic toilet and shower facilities, for the payment of a fee. Fossickers intending to camp should contact the landholder's agent at the camping area about 200m south-east of the Elizabeth Creek crossing. Camping is also not permitted elsewhere on adjoining properties. A range of accommodation is available at Mount Surprise.
The creeks are dry and water is not usually available on the diggings.
The rocks in the vicinity of O’Briens Creek are mapped as the Elizabeth Creek Granite of Carboniferous age. The granite is a pink medium-grained, and slightly porphyritic granite containing minor mafic minerals. Topaz and tin were deposited in veins and altered zones derived from late-stage melts and fluids during the cooling of the granite. These resistant minerals were liberated by erosion and later concentrated in creek alluvium and possibly hillwash. The area has been extensively worked for alluvial tin.
Topaz and other gemstones are found in alluvial gravels (wash), which are up to 2m deep, usually in present creeks and gullies. The wash consists of sand and gravel with some cobbles and boulders. Colluvial or hillwash deposits also have potential to be gem-bearing. Tailings from previous tin mining operations throughout the area offer further potential for gem finds.
Other gem materials found in association with the topaz are mainly the quartz varieties, rock crystal, citrine and smoky quartz, and the beryl variety, aquamarine. Fragments of cassiterite (tin oxide) are also found.
O’Briens Creek, Tourmaline Gully, Crystal Gully, Swampy Gully, Six Mile Creek, McDonald Creek and Lancewood Creek are the main areas of interest to fossickers (see map).
Digging with hand tools and dry sieving are the usual methods used to search for gems.
Several mining claims and two mining leases within the area are excluded from the declared fossicking area (see map); these must not be entered without the permission of the holders. Posts mark the corners of each tenure. Several residence areas exist along Elizabeth Creek (see map), which are also excluded from the fossicking area.