Abstract
Opal at Lightning Ridge typically occurs at the interface between the electrically resistive Wallangulla Sandstone and the deeper conductive Finch clay facies. The best quality opal is generally found beneath thicker portions of the Wallangulla Sandstone and associated with local jointing, faults and breccia zones. 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.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
