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About oro

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    Costa Rica
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    placer mining
  1. Basically I'm looking to buy a simple device (geophysical, not drill) to keep on hand, for simple estimates of depth to bedrock. I see simple devices for seismometers (earthquake) and for ground resistivity (electrical contractors) for other applications but my particular interest is for occasional measurement of depth to bedrock.
  2. Any placer miner these days knows there are several state of the art geophysical methods used in mineral exploration (gas and oil too), that determine a variety of characteristics of the subsurface in 2D and 3D outputs - by measuring resistivity, gravity, magnetism and other features such as depth to bedrock and contour, water table, sediment / gravel layers etc. - seismic units and ground penetrating radar to locate “anomalies”. The problem is these technologies are still expensive and out of reach of most small commercial scale placer miners and seem to require a high level of learning and deployment. But I sometimes think / dream about a simple device that would measure just one thing - depth to bedrock. I see some of the commercial seismic survey systems use a simple sledge hammer activator (striking plate) to send out a seismic wave which is picked up by a daisy chain of geo-phones and sent to a computer to record, analyze and display the data and images. I also see simple seismic detector devices to measure earthquakes for sale for under $500 (Infiltec / Amazon). I would think coupling the same sledge hammer activator to a simple seismic detector designed to measure one thing (depth to bedrock) would be feasible and inexpensive. Maybe even without a laptop / expensive software but rather a single digital output / display. Is this only in my dreams or does a device like this exist? I recently got a quote from Geotmetrics for an entry level seismic survey system… 25k + 5k for onsite training. So, I dream on. I’ve done a bit of placer sample drilling and it’s not cheap either. Maybe there are other ideas / methods for an inexpensive geophysical method to determine depth to bedrock. Any suggestions?