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  #1  
Old 03-16-2007, 04:35 AM
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ToddB64 ToddB64 is offline
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Default "Hot Rocks" Questions

I am looking for some technical information on "Hot Rocks", as they relate to metal detecting.

I have the Garrett Ace 250, in case this is pertinent to your answers.

What is the mineral composition of a hot rock ?

Does a hot rock have nonconductive and conductive properties ?

Does a hot rock have magnetic properties and if so, how does this affect the radio waves coming from the coil ?

When a hot rock is under the coil, how do you know it, i.e. what type of audio/visual signals announce it's presence ?

Is it true that a hot rock has more nonconductive minerals than the surrounding matrix, and is that what causes a metal detector to register it's presents ??

These are just a few questions to give you an idea of the level of my curiousity.

Thanks for any information you care to contribute.

Todd

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  #2  
Old 03-16-2007, 10:15 AM
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Default Re: "Hot Rocks" Questions

Alot of good questions. Unfortunately, I'm new to all of this, so I don't have an answer. but I will be back to read the responces.

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Old 03-16-2007, 01:10 PM
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Default Re: "Hot Rocks" Questions

Me to! I have lots of questions along the same line. Here in Kansas there is big money in finding the huge ones that you did up with heavy equipment. High nickle content?

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  #4  
Old 03-16-2007, 01:43 PM
TonyinCT TonyinCT is offline
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Default Re: "Hot Rocks" Questions

Basically a hot rock is a concentration of non-conductive material that is higher in concentration than the surrounding ground matrix. The detector is tuned to the ground and balanced to eliminate the minerals in the matrix. The hot rock , since it is in a higher concentration , will give a posative response ( beep ) when the detectors coil is passed over it when in motion mode. It will conversely give a null or negative response when in true all metal mode. Usually the meter if so equipped will peg to the right or give a higher than normal number reading ( usually 95 on an XLT or DFX). Sometimes you will get a hot rock signal , dig down and disrupt the concentration, run your coil over the spot again and get no reading. I think Funnyfarmman is reffering to meterorites which are metallic in composition. Hot rocks are not metallic.

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  #5  
Old 03-16-2007, 01:49 PM
early_americana early_americana is offline
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Default Re: "Hot Rocks" Questions

Tony, thanks for answering this and Todd thanks for asking!

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  #6  
Old 03-16-2007, 07:08 PM
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Default Re: "Hot Rocks" Questions

Good answer Tony.

Todd, you might ask why the name "Hot Rock"? Well, because there also are what are called
"Cold Rocks". They are almost the exact opposite of hot rocks and behave also opposite.

The cold rock is a pocket of mineralization that is much lower than the surrounding ground matrix. In metal discriminate mode, they don't beep at you so they are less troublesome.

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Old 03-16-2007, 09:52 PM
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Default Re: "Hot Rocks" Questions

Quote:
Originally Posted by TonyinCT
Basically a hot rock is a concentration of non-conductive material that is higher in concentration than the surrounding ground matrix. The detector is tuned to the ground and balanced to eliminate the minerals in the matrix. The hot rock , since it is in a higher concentration , will give a posative response ( beep ) when the detectors coil is passed over it when in motion mode. It will conversely give a null or negative response when in true all metal mode. Usually the meter if so equipped will peg to the right or give a higher than normal number reading ( usually 95 on an XLT or DFX). Sometimes you will get a hot rock signal , dig down and disrupt the concentration, run your coil over the spot again and get no reading. I think Funnyfarmman is reffering to meterorites which are metallic in composition. Hot rocks are not metallic.

Thanks Tony ! Good reply. Only I don't understand how non-conductive material can create a positive response. I thought only conductive metals could do this. Can you explain ?

Todd

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  #8  
Old 03-16-2007, 09:58 PM
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Default Re: "Hot Rocks" Questions

Quote:
Originally Posted by Rudy
Good answer Tony.

Todd, you might ask why the name "Hot Rock"? Well, because there also are what are called
"Cold Rocks". They are almost the exact opposite of hot rocks and behave also opposite.

The cold rock is a pocket of mineralization that is much lower than the surrounding ground matrix. In metal discriminate mode, they don't beep at you so they are less troublesome.
Thanks Rudy ! I had that question on my mind and then forgot to include it in my post.

Todd

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  #9  
Old 03-17-2007, 12:49 AM
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Default Re: "Hot Rocks" Questions

My girlfriend wants me to save all the "hot rocks" I get.
I told her they usually just make me mad when I find them. lol.
She seems to be facsinated with them.
She keeps them all, and wants to use them in her garden area.
She's out of her mind.
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  #10  
Old 03-17-2007, 01:09 AM
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Default Re: "Hot Rocks" Questions

BFM........Ask her if those rocks stimulate.......a-hummmmmm......plant growth.

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  #11  
Old 03-17-2007, 12:38 PM
TonyinCT TonyinCT is offline
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Default Re: "Hot Rocks" Questions

Good Question Todd. The way I understand it is : Since you are "tuning" the detector or balancing it to the ground minerals and you use motion Discrimination , the hot rock is out of phase with the ground matrix and therefor causes a posative response just like a non-ferrous target. When you switch over to true all metal which is pure ground balancing , the detector is out of phase with the hot rock in the opposite direction and you get a nulling response. This is also how discrimination works on ferrous targets as opposed to non-ferrous. Its the phase of the material that comes into play. I think
Never have been real good at explaining all the technical stuff.

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  #12  
Old 03-17-2007, 04:43 PM
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Default Re: "Hot Rocks" Questions

Quote:
Originally Posted by TonyinCT
Good Question Todd. The way I understand it is : Since you are "tuning" the detector or balancing it to the ground minerals and you use motion Discrimination , the hot rock is out of phase with the ground matrix and therefor causes a posative response just like a non-ferrous target. When you switch over to true all metal which is pure ground balancing , the detector is out of phase with the hot rock in the opposite direction and you get a nulling response. This is also how discrimination works on ferrous targets as opposed to non-ferrous. Its the phase of the material that comes into play. I think
Never have been real good at explaining all the technical stuff.

Thanks again Tony ! This is getting interesting !! :spin: Personally, I think you have a lot of technical
knowledge and have been a great support to the members here for a good long time !

Todd

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