Comparing Minelab’s SDC/GPX/GPZ Detectors

Even though most goldfields have been worked over by Minelab Pulse Induction detectors for as long as I’ve been detecting, there’s still productive areas that will produce gold to anyone prepared to put in the effort, especially when using the newer SDC 2300 and GPZ 7000 detectors, or even a finely tuned GPX. Everywhere I go, people often ask for my advice on what they should buy, and after talking through the features and benefits, price, accessory options etc. some ask the very good question of: “Well, what am I likely to find with each unit?” There are so many variables here that it’s impossible to give a definitive answer that holds true in different locations, so let’s take a look at the ‘big three’ and see what they have to offer.

SDC 2300  – “The Hoover”

If you like the idea of a compact, waterproof, easy-to-use machine that has the potential to find gold in most old well worked areas, then this is a good choice.  It’s great for shallow ground, high mineralisation, charcoal infested areas, old diggings, surfacing, rough or specimen gold, backpacking into hard to access areas, and when it's raining and you just have to get out for a swing! Here are some examples of what I’ve found myself and typical finds reported from Australia and USA. 

No other detector can match the sensitivity of the SDC in highly mineralised soils. Actually, the more mineralised the better, as that is where previous detectors struggle the most, particularly on very small targets. I have been around detectors for a long time and, I can honestly say I’ve never seen so many people finding so many pieces of gold. Sure most of it is quite small, but gold is gold. Now, here’s the best news – it isn’t just the pro’s finding it. Total beginners to the hobby are getting their fair share too, because this unit is probably the easiest gold detector to use and runs so smooth in mineralised ground with virtually no false signals. There are a few limitations though. You can’t change the coil, so chasing big deep gold with an SDC isn’t going to happen. There is no iron reject, so if you come across a very trashy area, you either dig everything, or move on. There is also no volume control, but aftermarket accessories are available.

With the GPX 5000, I’ve found much fewer nuggets compared to the SDC 2300, but the combined weight of the pieces found was still higher than the SDC. Again, here are some examples of what I’ve found myself and typical finds reported from Australia and USA.

The GPX 5000 is compatible with Minelab Commander coils and a huge selection of aftermarket coils in a range of sizes, shapes and configurations. Closed, Open-web, Monoloop, Double-D, you name it. This allows you to customise the performance of the detector and also to your personal hunting style. If you like going over old workings, you may prefer a small round coil, or if you’re more of a patch hunter, you’ll probably opt for a mid-sized elliptical coil.  Of the big three, the GPX 5000 is the only one to offer an Iron Reject function. While most prospectors preach the “dig everything” approach, I bet you that every prospector has walked away from a certain spot thick with iron trash with plans to return for a better look but never has. I know I’m guilty of it! This is where you can strap on the stock 11” DD coil (or smaller DD), and select the High Trash Search Mode. You won’t reject every bit of iron, but you will ignore a large percentage of it, at least giving you some idea of what non-ferrous targets may be lying around in amongst the junk.  From salty soils, to extreme mineralisation, to very mild soils, the GPX 5000 has you covered! The Salt Gold timing on the GPX 5000 is very good, and allows me to use a mono coil on the wet sand flats on my local beaches – for times when I’m in the mood to dig some deep holes! 

GPZ 7000 – “The Beast”

Looking at the finds I’ve made with the GPZ during 2015, I found slightly less number of nuggets compared to the SDC, but the overall weight was much higher. If I counted how many 1 gram nuggets I’ve picked up with the GPZ compared to the SDC, the GPZ would be leading the race 10:1! Again, here are some examples of what I’ve found myself and typical finds reported from Australia and USA.

The GPZ 14 coil teamed up with the new ZVT technology is quite amazing. In the factory default settings you can be finding very small gold, and big deep gold without any setting changes, all with the one coil. The GPZ 7000 auto tracking is extremely efficient, and together with the Super-D coil has almost eliminated the possibility of tracking out a target. Using the detector in Auto provides consistent depth, reduces ground noises, and lets you get on with the job of listening for the next signal.

The GPZ 7000 is simply dynamite on what I call host rock gold. Basically gold that is still in its host rock or material, or only partially begun to separate itself – if you look at most of the gold being found with the GPZ, there are a lot of pieces still in ironstone, or quartz specimens etc. 

So how do they compare side-by-side?

In late spring of 2015, I organised a tag-a-long trip for a small group of keen South Aussies across the border to some of my favourite spots in Victoria. There was a range of Minelab units being used, and at the end of the 3 days, by rough tally I estimate that over 50 nuggets were found. Looking at the results from each detector, the SDC 2300 did the most damage on old surfacing areas and found the most number of nuggets overall for the trip, but ranked lowest in the total weight count. The GPX’s (3 x 5000s, 1 x 4500 and 1 x 4000) found fewer nuggets compared to the SDC 2300, but the combined weight of the pieces found was higher than the SDC, with several bits in the 0.5gram to 2 gram range being uncovered.  The gold found by the GPX’s definitely tends to be heavier, even though they can still ping bits below 0.1 grams. Of only two GPZ 7000’s being used, they found the most number of pieces, and also most weight overall. The other interesting observation was that the GPZ’s didn’t really care what form the gold was in: prickly, solid, flat, lumpy, ironstone specie… it pinged it all!

To find out more about Nenad Lonic and Phase Technical visit www.phasetechnical.com.au. (The full article on which this blog is based has previously been published in Gold Prospecting magazines.)