Occurrence of silica in the natural waters of the Huntley-Robertson district, southern New South Wales

Abstract

The silica concentrations of both ground and surface waters from the Triassic Hawkesbury Sandstone were found to range from 3.0 to 12.0 p.p.m.

Samples of soil, surface bedrock, and fresh core material were leached with water, and the results of chemical analyses carried out on the subsequent solutions are discussed with reference to the source of the silica in solution.

A time study of the release of soluble silica from sandstone indicated rapid dissolution within the first few days, with equilibrium concentration being reached after a period of several weeks due to inhibiting surface reaction on the mineral grains.

A possible explanation, based on the effects of weathering and the impervious nature of the sandstone, is suggested to account for the similarity between the silica concentrations of surface water and groundwater.