The gravel layers are often interlayered with coarse and fine sediments and vary from a few centimetres to over a metre thick and may rest on basement rocks. The smaller Lava Plains field differs markedly from the Anakie field in that the basalts that host the sapphires are very much in evidence on the field. The field lies within one of several major basalt provinces in northeastern Queensland, the McBride Basalt Province. Sapphires occur in eruptive volcanics from a limited number of vents and are recovered from the eluvium, colluvium and alluvium within and adjacent to present day watercourses in the vicinity of the vents. The sapphires occur in brown and black clayey soils containing vesicular basalt rock fragments and basalt cobbles and boulders.
Associated minerals found in the wash include zircon, ilmenite, olivine, hematite and feldspar.
The main areas mined are centred on Wyandotte Creek and Mines Hill. Processing wash to concentrate the sapphires and the heavy minerals also varies from rudimentary hand sieving and washing to more sophisticated mechanised plants. Queensland s production of sapphire is mostly from the Anakie field in central Queensland. There has been no commercial mining undertaken on the Lava Plains field since 1993, but recent interest by miners indicates that some production is likely to restart shortly. Sapphires mined are a mixture of dark blue, parti-colours and fancy stones.