I have finally gotten around to processing the samples I brought back from Cache Creek, a historical gold mining area that is now open to public access.
I had been sweeping areas with my Garrett AT Gold Pro metal detector and discovered two "hot rocks". These can be rocks that are high in mineral content, but using the detector's discrimination mode, the machine reported metal content and not iron.
I threw the rocks in my bucket, and to be safe, I dug up the dirt under and around the rocks for sampling later. The soil was wet, so it has been sitting indoors for a month or so, drying out.
First, I examined one of the rocks for any visible iron or pyrite. I did not notice an abundance of either.
🔗 [Link: flic.kr/p/2rK5Wei/]Next, I checked it with a very specialized metal detector, the Falcon MD-20.
🔗 [Link: flickr.com/gp/203623445@N04/7jc7jDcg59/]Unlike standard metal detectors, the MD-20 is a handheld unit used for testing samples or searching for gold embedded in rocks. I mostly use it to check seams in boulders looking for gold veins, or on exposed bedrock in rivers to locate gold trapped in cracks and crevices.
This detector is extremely sensitive, as it is designed to detect very tiny specks of metal. In the photo above, you can see the size of the detector in relation to the standard-size business card. Laminated into the face of the business card are three tiny specimens: pyrite, gold, and magnetite (black sand).
🔗 [Link: flickr.com/gp/203623445@N04/B68n8eZiWa/]You can get an idea of how sensitive the machine is by the size of these test samples that are used for calibration. You must be careful how you hold a sample for testing because the probe will detect the iron in your blood in your hand.
The end of the probe is adjustable for calibration. Think of it like a flashlight with an adjustable lens. When highly focused, the beam is very small and very intense. At that setting, the machine becomes sensitive to the Earth's magnetic field and has a difficult time remaining stable. At the other end of the adjustment, the beam is wide and less intense. It is very stable, but not as able to detect very small gold specks.
Testing my rock sample revealed that it does contain gold!
So the next step is to discover if I can see it, or if it is clusters of near-invisible gold crystals. If it is visible, I can crush the rocks and pan out the gold. If it is too small to see, then it is too small to bother with. (Been there, done that. No fun.)
Under the stereoscope, I can see some shiny, but they are pretty small. The camera mount for the scope doesn't work with my new iPhone, so no pics from there.
However, our very own
@Jessica_Rose showed me a mini desktop microscope camera that she has, and I just had to have one. It allows viewing on an LCD screen and can take pictures and videos through the microscope. Here is what I found in my rock sample.
🔗 [Link: flic.kr/p/2rKbPVg/]
🔗 [Link: flickr.com/gp/203623445@N04/3e9yVw317q/]
🔗 [Link: flickr.com/gp/203623445@N04/xM0s6A0G2A/]
🔗 [Link: flickr.com/gp/203623445@N04/95BU37o7m1/]Pardon my fat thumb.
The next step will be to crush the rocks into fine gravel and start panning them to see just how much gold is in there. I will also screen the dirt I scooped up and pan that as well.
I don't expect to find much, but I have been surprised before, so fingers crossed!
