Hot Rocks And Low Numbers

[Gatev]

hello friends, yesterday was a very nice day with very good finds. Despite the presence of hot rocks in the soil, which gave me a lot of false signals, I made a ground balance on such a stone and things were fine, there were false signals again, but they were recognizable very easily. VDI numbers jump over different ranges, and when I pass the coil over the fake object at 360 degrees, the color signal disappears and only the iron remains, so I divide it and avoid it. I found two silver coins that lifted my adrenaline. for European boys who go to Roman fields, do not avoid ID 6 to 10 because the ancient metal and coin sizes give different numbers when they have a lot of patina and a smaller size give low numbers. I am very pleased with NOX, I keep going. Greetings

[Steve Herschbach]

My hot rocks, which are iron mineralized rocks, ring up at -9, -8, and some at -7. The worst ones will give flashes of higher numbers but as you have noted they are easy to recognize due to inconsistent signals. At least in the location I last worked. Hot rocks are just “out of place” rocks that do not match the ground balance setting and so they vary depending where you are. Most naturally occurring hot rocks will read as iron but there are conductive hot rocks that will read consistently positive. Coke may look like a hot rock to many people, and it will typically ring up as a +1 or +2 reading.

This book is on gold prospecting and has a great section about hot rocks:

Gold Prospecting with a VLF Metal Detector by Dave Johnson
Chief Designer, First Texas Products & Fisher Research Labs
March 2010 Edition
 
This book explains how to use a VLF metal detector for finding gold. The author has nearly 30 years’ experience in the metal detector industry working for several different companies, and designed several of the most popular “gold machines” on the market. These include the Tesoro Lobo, White's GMT and MXT, and of course the Fisher Gold Bug and Gold Bug 2. Although the product emphasis is on the machines currently “Made in El Paso”, the features of competitors’ machines are also discussed. This booklet is useful no matter what brand of metal detector you use.
 
pdf download 29 pages https://www.detectorprospector.com/files/file/53-gold-prospecting-with-a-vlf-metal-detector/

 

[Gatev]

Thank you very much Mr.Herschbach ! 

I took a small piece of the mineralized rock and these days I will perform tests by placing different objects below it. I will describe the tests here.

[Steve Herschbach]

In the nugget detecting I have done so far with the Equinox it offers quite a toolbox. Multi-IQ packs a lot of punch. The good thing there is it is crazy powerful on tiny low conductors. The bad news is it will also “light up” hot rocks very well.

For this kind of work I have been favoring Gold Mode and Field 2. Gold Mode in particular will get those hot rocks while in Multi-IQ. Lower gain helps a lot because hot rocks typically lose signal strength faster than metals.

I prefer to hunt “wide open” with no target id numbers blocked if I can get away with it. This gives me stronger hits across the board, and most hot rocks exhibit as -9, -8, or -7. However, this can require too much work when the hot rocks are more plentiful. I will then block those three target id numbers.

Even then certain hot rocks will signal, and the ones that throw off oddball positive id numbers can get problematic.

For Gold Mode the solution for me has been to go to 40 kHz or 20 kHz. Both are very strong, easily matching dedicated nugget detectors for power. The good news is many hot rocks that bang hard in Multi-IQ get very weak in single frequencies, with minimal sensitivity lost on tiny low conductors. It really cleans things up in some places going to single frequencies.

Finally, since Gold Mode lacks target tones, going to Field 2 and using the solutions above plus the additional possibility of tones is another alternative. Instead of using Gold Mode and blocking the lowest target id numbers they can be left open to signal as ferrous or mixed ferrous targets. And you now have 5, 10, and 15 kHz options that Gold Mode lacks.

Hot rocks act as “masking targets” that hide good items under or next to them. Be sure and use faster recovery speeds in thick hot rocks to better see between them.

Still learning....