DATE: Wednesday 19 September 2001

Electrical, electromagnetic, magnetic, induced polarisation and seismic reflection surveys have all been trialed by the New South Wales Department of Mineral Resources at Lightning Ridge. The electrical and electromagnetic methods appear to provide a means to define the conductive Finch clay facies (or "opal level"), the overlying and moderately resistive Wallangulla Sandstone and the highly resistive surface gravel and silcrete (or "shincracker") layers. Localised linear features appear to be well-defined in both TEM and high-definition ground magnetic data as electrically resistive and high frequency magnetic anomalies. Results indicate that an ultra-detailed airborne electromagnetic survey may assist in the future search for opal at Lightning Ridge.

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