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Steve Gholson

SD2100 - SD2200 - GP Extreme!

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Hello everyone,


I have watched with keen interest the debate that continues on most

of the forums about the Minelab SD series of detectors vs. the GP

Extreme and thought the data enclosed might be of some interest.

While in Western Australia in 2001, Chris G. and myself joined up with

a group of prospectors and spent some wonderful time out bush looking

for the yellow metal and enjoying the company of some colorful characters.

Each evening everyone would gather and weigh the gold that was

found that day by each prospector and listen to all the wild tales of how

good we all were at detecting. As you can imagine, there were lots of

laughs and plenty of embellished stories regarding hole sizes, hole depth,

faint whispers, etc. etc...


While the data is not scientific, it is a true representation of the actual

finds out on the goldfields. To my knowledge, there was no other machine

being used other than the SD2100,SD2200 and the GP Extreme. All prospectors

were hunting the same area’s and spending approximately the same amount

of time each day out in the field. I would estimate that each prospector

spent a minimum of six hours detecting each day for ten solid days.

If we consider that there were 31 operators, the total man hours spent in

the field would equal 1,860 hours (31 X 6 X 10 = 1,860 ). This data was

generated from those 1,860 hours on the goldfields.


There are at least two important variables that were not gathered at that

time which would have an impact on the final data. Unfortunately the

coil information (size & type) could not be accurately recorded as some

operators were switching back and forth depending upon the conditions.

Also, the experience of each operator was hard to judge and subjective

in nature.


I have presented the data in one form but you can take the numbers and

generate lots of things to look at. This information is presented here only

to give you some more “ammo” that you can use in your debates regardless

of which type of machine you prefer.


-Steve Gholson



Total number of prospectors = 31 100% (percentage of total)

GP Extreme users =10 32% (percentage of GP Extremes)

SD 2200 users =13 42% (percentage of SD2200’s)

SD 2100 users =8 26% (percentage of SD2100’s)


Total number of days prospecting = 10

Total amount of gold found = 815.9 grams, ( 26.2322 Troy ounces).

Total number of nuggets found = 394


Average weight per nugget = 2.0708 grams, (all machines, 815.9/394).

Average wt. per nugget, GP Ext. = 2.3156 grams

Average wt. per nugget, SD2200 = 1.818 grams

Average wt. per nugget, SD2100 = 2.0284 grams


Average weight of gold per day = 81.59 grams (all machines, 815.9/10)

Avg. wt. of gold per day, GP Ext. = 37.05 grams

Avg. wt. of gold per day, SD2200 = 25.27 grams

Avg. wt. of gold per day, SD2100 = 19.27


Avg. number of nuggets per day = 39.4 (all machines, 394/10).

Avg. # of nuggets per day, GP Ext.= 16

Avg. # of nuggets per day, SD2200= 13.9

Avg. # of nuggets per day, SD2100= 9.5


Total amount of nuggets found = 394 (all machines).

Total amt. of nuggets found GP Ext= 160 ( 40.61% of all nuggets found)

Total amt. of nuggets found SD2200= 139 (35.28% of all nuggets found)

Total amt. of nuggets found SD2100= 95 ( 24.11% of all nuggets found)


Total amount of gold found = 815.9 grams (all machines).

Total amt. of gold found, GP Ext. = 370.5 grams (45.41% of all gold found)

Total amt. of gold found, SD2200 = 252.7 grams (30.97% of all gold found)

Total amt. of gold found, SD2100 =192.7 grams (23.62% of all gold found)



Total weight of gold and quantity of nuggets per day, (all machines).


DAY, Weight (grams), Quantity of nuggets

1, 55.4, 45

2, 68.7, 44

3, 111.6, 67

4, 60.7, 34

5, 4.3, 5

6, 53.7, 27

7, 79.5, 40

8, 167.4, 50

9, 80.9, 33

10, 133.7, 49

------------- ------------

Total 815.9(grams), 394(quantity)


Total weight of gold per day for each machine.


Day, (Grams per machine)- SD2100, SD2200, GP Ext.

1, 4.5, 36, 14.9

2, .8, 22.1, 45.8

3, 42.6, 26.2, 42.8

4, 17.6, 18.9, 24.2

5, 0, .2, 4.1

6, 21.9, 11.5, 20.3

7, 9.6, 17.5, 52.4

8, 19.1, 19.5, 128.8

9, 19.7, 53.9, 7.3

10, 56.9, 46.9, 29.9

---------- ---------- --------

Total 192.7 (2100), 252.7(2200), 370.5(GP)


Total quantity of nuggets found per day for each machine

Day, (Quantity of nuggets)- SD2100, SD2200, GP Ext.

1, 6, 25, 14

2, 2, 20, 22

3, 26, 17, 24

4, 8, 10, 16

5, 0, 1, 4

6, 7, 7, 13

7, 8, 9, 23

8, 15, 11, 24

9, 7, 18, 8

10, 16, 21, 12

Total ---------- -------- -----------

95(2100), 139(2200), 160(GP)



Data for each prospector by name


Name, Weight of gold(grams), Quantity of nuggets, Machine type

Steve G., 64.1, 34, GP Ext.

Chris G., 61.8, 35, GP Ext

Bob A., 57.1, 13, GP Ext.

Doug S., 53.9, 15, SD2100

Erik M., 51.9, 24, GP Ext.

Spencer, 50.2, 40, SD2200

Bryan, 37.4, 12, SD2100

Dave A., 36.1, 14, SD2200

Ken D., 34.1, 16, SD2200

Tony, 32.5, 24, SD2200

John F., 32, 12, GP Ext.

Peter, 29.9, 3, SD2200

Hermann, 28.8, 24, GP Ext.

Graeme, 28.7, 7, GP Ext.

Peter P, 28.2, 14, SD2100

Phil B., 25.6, 6, GP Ext.

Mary P., 21.6, 12, SD2200

Alan, 21, 10, SD2100

Orlando, 20.5, 16, SD2100

Graeme P., 18.6, 18, SD2100

Bruce, 18.5, 2, GP Ext.

David E., 16.2, 11, SD2200

Charlie, 15.7, 10, SD2200

John A., 10.8, 4, SD2200

Peter Dean, 6.6, 3, SD2100

Ray, 6.5, 7, SD2100

Chuck, 4, 3, SD2200

Vic W., 2, 3, GP Ext.

Tom T., 1.6, 2, SD2200

John M., 0, 0, SD2200

Kim, 0, 0, SD2200

------------- -------------

Total = 815.9(grams), 394(quantity)


Top five weight producers and their machine type


Steve G. 64.1 (grams) GP Extreme

Chris G. 61.8 GP Extreme

Bob A. 57.1 GP Extreme

Doug S. 53.9 SD2100

Erik M. 51.9 GP Extreme


Top six nuggets producers and their machine type


Spencer 40 (nuggets) SD2200

Chris G. 35 GP Ext.

Steve G. 34 GP Ext.

Erik M. 24 GP Ext.

Hermann 24 GP Ext.

Tony 24 SD2200


Top two weight producers for each machine


Steve G. 64.1 (grams) GP Extreme

Chris G. 61.8 GP Extreme

Doug S. 53.9 SD2100

Spencer 50.2 SD2200

Bryan 37.4 SD2100

Dave A. 36.1 SD2200


Top two nugget (quantity) producers for each machine


Spencer 40 SD2200

Chris G. 35 GP Extreme

Steve G. 34 GP Extreme

Tony 24 SD2200

Graeme P. 18 SD2100

Orlando 16 SD2100


Top five best day total weight results by any machine


128.8 (grams) GP Extreme

56.9 SD2100

53.9 SD2200

52.4 GP Extreme

46.9 SD2200


Top five best day total nugget (quantity) results by any machine


26 (nuggets) SD2100

25 SD2200

24 GP Extreme

24 GP Extreme

23 GP Extreme



Partial summary;


Total gold found = 815.9 grams

Total number of prospectors = 31

Average gold per prospector = 26.32


It would be expected that an average or above average prospector should find

at least 26.32 grams. The following analysis is based on any person with any machine that found at least 26.32 grams of gold. Out of the 31 prospectors that were detecting, 15 of them found at least 26.32 grams of gold. The total amount of gold found by these 15 prospectors was 626.7 grams which represents 76.81% of the total gold found by all of the prospectors. This means that approximately 50% of the prospectors found about 77% of the total gold found within the group. By using 26.32 grams of gold as our reference, the data below should be a better representation of how each type of machine preformed. Generally speaking, the new or inexperienced operators should be eliminated from the final data.




Total prospectors above 26.32 grams = GP Extreme, SD2200, SD2100

7 out of 10, 5 out of 13, 3 out of 8

70%, 38.46%, 37.5%

Total gold found 324.4 grams, 182.8, 119.5

Average gold per machine 46.34 grams, 36.56, 39.83

Total quantity of nuggets 149, 97, 41

Average quantity of nuggets 21.29, 19.4, 13.67

Average weight of nugget 2.177 grams, 1.884, 2.915

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Really enjoyed your detailed and informative post Steve,thank's for a major effort!



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Hi Steve,


Interesting numbers, would it be possible to come up with an average percentage of the GP compared to the rest and then call that the performance gain over all the others? As I am a realist I feel this would be being unfair, because there are so many variables. Still (as I see it) the overall trend is very much in the favour of the GP extreme.


One thing to consider is the more experienced operators should have been using GP's, although going by some of the names I recognise I see that at least two are using SD2100's, which is interesting. Another thing to point out is the SD2100 produced more sizeable gold (going by the average weight per numbers); could this be because of a lack of sensitivity to the smaller gold? If an operator doesn't get anything in an area that is producing lots of smalls they will generally gravitate away, there by increasing the chances of larger gold. You only listen for what the detector tells you.


I have experienced this plenty of times when Frieda and I used to use the VLF machines. I used a Whites Goldmaster Vsat and Frieda the XT17000, I would always without exception find the most numbers of gold and she, much to my frustration would find equivalent or better weights. The Whites had incredible sensitivity to small gold but didn't punch deep in heavy mineralisation; the XT on the other hand handled mineralisation very well. Different shovels for different holes I suppose.


Jonathan Porter

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That is an excellent report and just the kind of "hands on" tests that are needed IMO.


I'm sure many will say there are still too many variables that will make the results skewed this way or that...but I think part of the strength of a test like this is it gives a good idea of "average" results from a cross section of user styles,experience levels,coils used,etc.


In statistics there is a somewhat agreed upon number that they use when doing sampling techniques and that number is generally 30. Any less than 30 samples and you have to allow for larger levels of error in the results. One good thing about this test is that there was a good sized sample of users and machines used.


I would imagine the patience levels,experience, and swing styles of the users in the tests was a good broad mix which would...in my opinion make for a good general idea of what you can expect to attain with the detectors.



The fact that this test was done over many days in different areas gives the results even more validity in my opinion. This wasn't just a simple one hour or one day test in one area over one set of conditions. I imagine the conditions varied quite significantly in places.



I'd like to see more of these kinds of tests actually, maybe with a few VLF machines like the MXT,XT18000, Eureka Gold,X5,GMT,Goldbug 2,Tesoro LST and a few PI machines like the Infinium and Goldquest SS thrown into the mix. It would be nice to see how the other machines stack up to the Minelab heavyweights.


We would then see just what kind of perfomance gains to expect when users move up from VLF machines up to the PI machines...just what would the increase be in terms of nuggets found and total weight of nuggets.


A person could then put some type of "value" on what the step up from a VLF to a PI machine is worth.

For example...if a person is a casual user you can get an idea of what the break-even point would be in terms of how many hours per year you would need to spend swinging a detector to make the choice of a GP Extreme over a Eureka Gold a wise choice.


I would imagine the results in general would show more small nuggets found by the VLF's but more total weight by the PI's...but until more field use tests such as this one

are done..all we have is speculation.



Thanks again for sharing the results with us all, they are very interesting.

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A lot of interesting information in the tests.


I was just doing a few calculations from the results of the 10 days.


Just out of curiosity I figured out the "wages" that you could expect to earn by detecting with a SD2100/2200/GPExtreme...



Total ounces of gold found was: 815.9 grams/31.1 grams per troy ounce =26.23 troy ounces


Total Man-hours spent detecting = 10 days X 31 users X 6 hours per day =1860 hours


Wages "earned" per hour spent detecting = (26.23 ounces X 337 US$ current spot gold price) / 1860 hours = $4.75 US$ per hour


4.75 US$ = 8.00$ AUS = 4.46 $EURO =7.03 $CDN = 8.65 $NZ =3.03 $GBP



I just thought it would be amusing to see what kind of "wages" a person could average nugget detecting in reasonably good nugget producing ground over a significant amount of time.


This gives a person somewhat of an idea of just how long it might take to pay off of that new Minelab SD2200 or GP EXtreme :unsure:

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Hey Darren,


Is that before or after taxes? :D


It's apparent that you are a bit of a mathematical whiz yourself. I can hardly wait to see what you and Steve will be cooking up for us in the future - great post!!!


Chris Gholson

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