How do you determine if your soil is hot?

I just moved to Southwest Virginia.A lot of the soil appears to be red clay)laterite?).How can you accurately "measure or determine the degree of the mineralization?I have a F 75,F70,F5,CZ70,Explorer Se with a Pro coil and a Sov.GT.I've only taken the F75 and F 70 out hunting some playgrounds/soccer fields.Thanks Bill

that gives the relative values for the FE304 meter. It ranges from blank to 3. 3 is HOT HOT HOT, and 0 is pretty much the absence of mineralization.
the increments go in multiples of three. In other works any particular reading is three times what the one below it is. In the area around cupleper Va, the FE304 reading varies from .1 to 1, with the RARE 3. The thing to remember when evaluating your ground, is that the GB reading will tell you the TYPE of mineralization, and the FE304 meter will tell you the AMOUNT (severity). My soil for instance HERE is pretty mild. 60/65 on the Gb depending on ground moisture, and mostly .01 to .03 on the FE304 meter. Sometimes there is NO reading on the FE304, but usually I'll get at least one bar. I consider my soil "common".
Streak!

Streak,

That's correct. After this; In furtherance, the ultimate test is to find some fairly 'hot' ground..... and bury a clad dime at 4"........then 5".......... then 6"..... and see when each detector starts to fail at proper ID. You will (most probably) find the Minelab Explorer being the winner...retaining proper/accurate ID ....to greater depths....in this bad-ground.

Tom

Hi Kim, those are exactly the same readings I get at the Saxon church field.

Kickback, It would be Intresting to get the Difference in Performance Between the Minelab and F75..I was Told by several Folks to get the Minelab over the F75 Due to the Red Clay NC Ground I have Here..But I went against the Grain and Went for Speedy...F75..And love it..

if memory serves me, tecting around where you live is pretty much the same as the ground conditions here, cept at the field at the mad farmers (Ians) where all those romans had that iron encrustation! Wasnt that field flooded for many many years??

It was, and has been an exremely wet field up until the last 5-6 years when he put drainage in.
It is under wheat at the moment for the next couple of weeks until harvest.
It will be a good field to try the F75 and to see what readings it gives on those bronzes. It has had 2 ploughings since I last went on it.

First time poster........long time lurker here. Quick question. I understand the FE304 meter indicating the amount of mineralization on the F75. I am a little confused on the GB# telling you what kind of mineralization you have. Is there a list of some kind that relates this information as to what GB number represents the type of mineralization???

I will be getting a used F75 from Streak this week and was would like to know what kind of mineralization my gound here in East Texas contains.

Great forum by the way!

The information you seek is in the manual.

All different soil types will Gb a bit different,(higher or lower) on soils ranging from salt to magnetite (black sand). The Gb number the machine settles on will tell you (generally speaking) what type of soil you have in your area. There is a good chart in the F75 manual that coveres this well(both for the Gb setting and FE304 reading), and when you get the machine you should have a peek at it. The GB numbers along with the FE304 reading will give you a pretty accurate indication of where you stand soil wise, and then you can tailor your tactics accordingly. Good to see you here!! Streak!

Ok..........thanks guys! I guess it would help to have the manual. Strange...I have several other detectors and none of them have ever given any information on what the GB# represents. I guess they expect you to figure that out for yourself.

Thanks Streak! We head to Colorado bright and early in the morning. Can't wait to get out of this darn 110 degree oven called Texas! I will be looking forward to getting my hands on that F75 and manual.......when I get back home.

Hi Kickback,

Bill, about the Fe3O4 bar graph and how it should be interpreted by comparison with the ground phase equivalent GB scale readout. I wondered if you might be looking for a more detailed overview. The following represents my understanding on the subject, based on testing various iron minerals over the years.

The bar graph indicates magnetic susceptibility only (dependent upon both type and amount of ground mineral...the respective manuals [GMT & F-75] do not fully address the subject in my view). The ground phase (described by engineers as a “non-linear numerical mapping of magnetic loss angle”) reading indicates the overall “type” of iron mineral(s) that may be present in a soil. As noted in posts above, the manual contains general information regarding soil types represented by various ground balance ranges. Below is some background explanation...

The ground phase readout as represented by the GB scale normally does indicate type of iron mineral(s), but this is not exact science and therefore does not necessarily reflect any one given type of iron mineral. For an example, similar GB readings can be had from either (a) mixtures of magnetite and maghemite common in most soils, or…as an example…from (b) a very common hydrated iron oxide... goethite...which is quite prevalent in northerly latitudes and widespread in brown soils.

*********************************************

Background Information:

maghemite = high magnetic susceptibility, but also a high magnetic loss angle that can result in GB comp values ranging down into the low/mid 40's on F-75 GB scale...the range depending on impurities. Generally reads around GB50ish. Primary constituent of “positive” hot rocks (“zip zip” signal).

magnetite = higher magnetic susceptibility than maghemite, but has a low magnetic loss angle that results in GB comp values ranging roughly from GB75 and higher on the F-75 GB scale. Primary constituent of “negative” hot rocks (“boing” overshoot signal when using all-metal motion mode).

**********************************************************

Lets continue the example with the above background info in mind…

The big difference between the two iron mineralization examples used above (magnetite/maghemite mixture vs goethite) is that while able to generate a similar range of ground phase readings...the magnetite/maghemite mixture (or either one individually for that matter) will raise the magnetic susceptibility many times more than a similar amount of goethite (or other weakly magnetic iron oxides such as hematite, siderite, and hydrated iron oxides captured under the generic description of “limonite”).

Goethite, for example, demonstrates a relatively low magnetic loss angle (accounting for a moderate or slightly higher ground phase reading) but also demonstrates a low magnetic susceptibility. Thus it may ground balance well up on the F-75 scale, but have little effect on the Fe3O4 bar graph and detector performance (regardless of amounts) by comparison to magnetite and/or maghemite.

The above explanation aside, I suggest F-75 users (a) view the ground phase as a simple ground "target" measurement based on phase shift similar to any other (phase shift) target ID measurement for discrimination purposes...but of course in this instance...adjust the ground balance accordingly, and (b) view the Fe3O4 bar graph results that are (only) merely expressed as % volume magnetite...as a measurement of magnetic susceptibility that results from any iron mineralization present. This measurement may or may not actually include magnetite (although the absence of any magnetite in most soils would be highly unusual), depending on ground iron mineral composition.

As pointed out above, as the level of the Fe3O4 graph readout increases…the “hotter” the ground…which means… more highly magnetic susceptible ground, and thus more difficult ground to achieve good performance results with VLF units by contrast to performance in relatively lower magnetic susceptible soils.

Hope this will be helpful to you Bill. Later,

Jim.

The accolades of well-orchistrated white paper eloquence. Thanks Jim!!!..... for your blood, input, time, clear/definitive explanation in this lesson of Geophysics. If only some of your talent were to be utilized as a Univ Professor on such subject matter. Priceless. With gratitude;

Tom

Thanks Tom, most kind of you.

Fortunately, we hobbyists exist in an informational community. I suppose the challenge is to distinguish good from not so good information, no matter how well intentioned. That said, we all can err on occasion. I do frequently, just ask my wife!!

Aside from yourself, credit for much of what I post must go to Dave Johnson, Carl Moreland, and Ty Brook. These gentlemen all have generously provided insights to me on various topics. Dave in particular is an invaluable resource. Aside from all else, his knowledge of metal detector response related to mineralogy...emphasis to iron minerals...is very impressive. A true pioneer, his research efforts have provided hobbyists with groundbreaking technology. And lets keep in mind your own research efforts Tom, and kindly sharing hard-won expertise with the rest of us. We detectorists owe you a debt of gratitude along with our enduring regard and support...now and ever. Thankyou,

Jim.

NASA-Tom Wrote:
-------------------------------------------------------
> The accolades of well-orchistrated white paper
> eloquence. Thanks Jim!!!..... for your blood,
> input, time, clear/definitive explanation in this
> lesson of Geophysics. If only some of your talent
> were to be utilized as a Univ Professor on such
> subject matter. Priceless. With gratitude;
>
> Tom
...I Totally Agree with Tom....Jim you have Taught me ooodles and ooodles about Detecting and minerals over the past few years. As you know My Time is very limited and its always a Hit and Run situation. Jim, Its good to hear your still in Contact with Dave Johnson..Good minds Think Alike..james

Jim
Thgank you.Your responce made this topic easier for me to understand.Bill

Bill, More than Likely Your in the same boat as me here in NC..Red Clay to Brownish Dark Clay..Its as hott as Fire Works on the 4th of july..I have found that a Good Ground balance is key to help the Cause and Often..

Jim,

You are to prospecting as I am to coin/relic/jewelry hunting. ---Taking things to the extreme.

Glad to have you both here...Best Info On the Net..

.....by virtue of 'burning passion'.

I think this answers my GB and Fe O question.

Great! And I'm glad you found it.

A thread worth reading again.



Edited 1 time(s). Last edit at 10/27/2011 10:44PM by gman.

Correct again Tom.
I have the new black F75 LTD and found it very hard to hunt with at some of my sites. I bought an Explorer and found great pleasure hunting these difficult sites. Then one day one of my hunting buddies wanted my Explorer regardless of price so I sold it and bought the Etrac. Wonderful machine. pleasure again, a lot to learn too. Now on the flip side, if I'm going gold hunting in the tot lotes the LTD is my companion because the Etrac just can see the smaller gold (small earrings) regardless of settings.

NASA-Tom Wrote:
-------------------------------------------------------
> Streak,
>
> That's correct. After this; In furtherance, the
> ultimate test is to find some fairly 'hot'
> ground..... and bury a clad dime at 4"........then
> 5".......... then 6"..... and see when each
> detector starts to fail at proper ID. You will
> (most probably) find the Minelab Explorer being
> the winner...retaining proper/accurate ID ....to
> greater depths....in this bad-ground.
>
> Tom

Mark you meant to put the " 't " on can, right?
I'm sure you did an air test with gold jewelry on the 75 and the E and the 75 came out slightly ahead.

Bump

What about this?? Let's say my so and so detector will air test a clad dime at 10.5 inches. I bury the dime in soil that has been purged of all other signals. And I barely hit the dime at 7 inches, and THEN it's just an iron grunt one way and a mid tone the other way. Guys, doesn't that give me some real-world data on the composition of my soil. Please bear in mind, and it's quite obvious I'm sure, that this question is the question of a one year man. A newbie. Me.

Kevin......... yes, that is correct........... and is one of the ways to tell how bad your soil is.