A new technique in finding crystal pockets is to use Ground Penetrating Radar (GPR) to detect differences in density associated with the air or clay that fills the crystal cavities. A portable radar emits pulses that can range from 500--1000 MHz. The pulses go into the rock and are reflected back by the various layers inside. A computer puts all the echoes from the layers into a format that can be interpreted (more or less!) as a cross section of what the radar is seeing. A crystal pocket may show up as an anomaly in the rock layers. This anomaly, combined with geological knowledge and skill of the operator can greatly enhance the search for crystal pockets.
Jeffrey Patterson, a doctoral student in geophysics at the University of Calgary and perhaps the world's leading authority on using GPR to find crystal pockets, has been some San Diego County's most famous mines. He has been very successful, finding several pockets and numerous small vugs containing gem tourmaline, quartz, and other minerals.
The following pictures show the radar in action and some of the pockets that have been found.
Jeffrey Patterson Scanning the Dike at the Little Three Mine
Line Rock at the Little Three Mine
Opening a Tourmaline Pocket at the Himalaya Mine
Journal of Geophysical Prospecting Preprint
Table of Pockets Found with Radar
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