Minelab Video - GPZ 7000 Gold Mode

[Steve Herschbach]

[Steve Herschbach]

I like this video because it adds a bit to the question asked at http://www.detectorprospector.com/forum/topic/806-zed-scores-big-on-civil-war-relics/?p=7845 about the Extra Deep mode.

This mode is really not named properly. The video makes clear that General is more powerful than Extra Deep and so under most normal circumstances Extra Deep will not go deeper than General. So what's up with that?

General as it notes in the video pushes the detector hard, and so it gets very good performance on small gold and the best depth on larger gold. However, it is also going to light up ground noise and hot rocks in the worst locations. And like everything metal detecting, depth is always relative to ground conditions (no air tests please).

This means that in severe ground Extra Deep will run quieter and allow large nuggets to be heard where with General they will be lost in the ground noise. Deeper in a relative sense, not deeper in an absolute sense.

Does that make sense?

They may have better called the modes Small, Medium, and Large. From a occurrence distribution standpoint small gold is always more common than huge nuggets so going for smaller gold does tend to be a High Yield strategy, as most larger gold will still be found anyway. Many areas will also be good for General when seeking the largest deep nuggets. But the so-called Extra Deep mode looks more useful on what it does not detect than in what it does detect. This will be a mode for attempting to pass up on annoying smaller targets or dealing with severe ground while still finding larger items. Severe ground mode is a possible option for very bad ground but it locks you into High Yield and so tends to be a last ditch method sacrificing deep targets. It appears to me a person may want to try Extra Deep and Difficult as an alternative to Severe when chasing very large gold in very bad ground.

[russ]

Thanks Steve,

 

It's interesting, Gold mode High Yield medium or small nuggets typical 0.1 grams to 50 grams.

 

I wouldn't call a 1.6 ounce nugget small or medium, at least not in Arizona. 

 

And General typical is 5 grams to 50 grams. 

[Steve Herschbach]

Did you catch in the video where they said High Yield for nuggets 1 oz and smaller?

 

The fact is it is a very, very fuzzy target trying to set size ranges. Round solid lump, or prickly specimen? Gold is just too variable in nature to put in tidy categories. Nothing but trial and error will reveal what works best in different areas with different mineralization and types of gold. But at least we can make educated guesses.

[russ]

Did you catch in the video where they said High Yield for nuggets 1 oz and smaller?

 

The fact is it is a very, very fuzzy target trying to set size ranges. Round solid lump, or prickly specimen? Gold is just too variable in nature to put in tidy categories. Nothing but trial and error will reveal what works best in different areas with different mineralization and types of gold. But at least we can make educated guesses.

 

Yes I caught that too when I watched it this morning.

 

Who are those guys?

 

Where's JP when you want him?

[mn90403]

Steve,

 

There is a difference between the video and their written descriptions of the modes.  There is one piece of literature that says Extra Deep is 40% deeper but that is not what they say in the video.

 

Mitchel

[Steve Herschbach]

I tried to explain it but I guess I did not make it clear. The GPZ is not going "up to" 40% deeper than itself when you switch to Extra Deep. It is going "up to" 40% deeper than a GPX 5000 under very rare circumstances involving extremely mineralized ground and very large gold nuggets.

Russ, kind of cruel sticking Minelab engineers in front of the camera. They are probably wondering where that was in the job description. I also wish for the JP version, but the engineers are more fun to talk to in some ways. They see things from an entirely different perspective. Really smart guys but not prospectors.

It is not very mysterious. Extra Deep is a mode for dealing with very bad ground while trying to find very large gold nuggets. In almost any other circumstances it is going to lose depth, not gain it. PI performance is relative to mineralization. Modes that improve performance in bad ground can cost you performance in milder soils.

At the end of the day naming it Extra Deep was a bad idea. It is however hard to name it anything in fact as any word or two is misleading. I tend to think of it as "Long Time Constant" mode myself. Then the 40% thing in the brochure (but not in the white paper) really messes with people. Everyone forgets the "up to". That is marketing fuzzy speak and from my perspective essentially meaningless. It is like EPA mileage figures "your performance may vary."

[russ]

I've only tried Extra Deep once with a quick test on a 1.5 ounce buried nugget. 

 

At 18 inches High Yield hit the hardest with General next and Extra Deep was the worst of the three gold modes so I've never used it again for hunting. Maybe the nugget wasn't big enough??? I should try a 6 ounce nugget a bit deeper but I think it would be the same outcome.

 

When Fred asked me what settings I was using on the GPZ I shared what I was doing and told him to stay out of Extra Deep. I wonder how many guys will have to re-hunt there favorite nugget patch now? I do know of a couple of washes loaded with ironstones I'll try extra deep on. 

 

As far as the Minelab video it just doesn't seem right to have guys that have probably never found a nugget before telling you how to do it... I could be wrong though. I would listen a whole lot more intently if a very successful prospector was teaching about the gold modes, guys that had actually had tried and true real world knowledge about the settings.  

[jasong]

Same here Russ, I tried an in ground test yesterday with my 47 gram slug and still couldn't get General to outperform High Yield at 20". The soil was bordering between Normal and Difficult, depending who you talk to. But General works in Normal so I don't see why there shouldn't still be an increase in depth on those big chunks even in medium ground.

 

I suspect the Ozzie concept of "big gold" is a bit different than ours. My nuggets are probably "fines" over there.

 

Side note: never call a physicist an engineer, I've seen fisticuffs over less.     Kidding, it's a running joke between the two.

[Jonathan Porter]

The two guys in the video are good friends of mine who are very passionate about metal detectors. Mark Lawrie on the right has spent considerable time with me in the field over the last few years and has found his fair share of nuggets along the way, Phil on the left is scarily bright (both guys are inhuman in this regard compared to my simple two dimensional brain), Phil did the main development work on the Gold Modes and also the Ground Balance Tracker, both of which still blow me away on how refined they are . I personally feel the Product Development guys having a say on the GPZ is a great idea as it gives people a further insight into the detector from the developers point of view, sure its a little stilted but the overall message is still extremely valid.

 

Putting anyone in front of a camera is daunting at the best of times, having them do it unscripted is testament to the amount of passion they have for the GPZ 7000.

 

JP