Prospecting for gold nuggets with White's versatile MXT metal detector; Part 4 FAQ

The MXT FAQ - Part 4

The MXT FAQ and Operation pointers PART 4 (FAQ Questions Nos. 21-28):

21) What should the gain setting be when detecting for gold?
One of the main keys to detecting small gold with the MXT is cranking up the gain to the +3 MAX. Having the 6 inch DD is also very worthwhile, both from the stand point that with its small size it is more sensitive to small gold, but also that it allows higher gain settings than the 950 coil under mineralized conditions. It is also less susceptible to changes in soil mineralization than the 950 standard coil. In doing some tests in my yard, I found I could barely detect a 0.5 grain flake with the 950 coil at a gain of +1 (with the flake is right on the surface about 1/2 inch below the coil) - the signal was there but was so weak that in the field, honestly I probably would have ignored it, or not been able to distinguish it from hot rock / background noise. A gain setting of +3 gave a much better response. The 6 inch DD gave a better response to the 0.5 grain nugget at all gain settings. At times, high and variable mineralization may make it necessary to reduce the gain, but when that happens, sensitivity to small gold will be reduced.

22) What does the iron probability reading in prospecting mode really mean?
When using the prospecting mode, probably anything that does not make the "grunt" sound (80% iron probability) should be dug. The target ID on the MXT is excellent, however it is not perfect. The ID does not work as deep as the detector will detect. In high iron soil areas, it is possible for small nuggets near the edge of their detection limit to score as high as 70% iron probability. In my experience, most junk iron gives a reliable signal with the special "grunt" sound. However, it you are looking for meteorites, the "grunt" noise may indicate a meteor. Use of a magnet to collect surface iron is also helpful. On the other hand, many small nuggets below about 2 grains weight do not give any ID indication. Tiny bits of iron or lead can also fail to give a VDI or probability response. Repeatable targets which do not give any ID should be investigated. if passing a magnet over the surface does not cause the target to go away by picking up any iron or small hotrocks, the target needs to be dug. The ID will not detect to the deepest and smallest of targets. The key is that if the target is repeatable, the magnet does not remove it, and does not seem to move around as the coil is passed over it, it probably is not iron (it is most likely lead or gold).
The iron ID in the prospecting mode should probably be interpreted as follows:
10 to 30% iron probability - The MXT is reasonably sure the target is not iron, dig these for sure.
40 to 60% iron probability - the MXT just can't tell - you will need to dig these targets or you will loose gold.
70% iron probability - in low mineral areas, you may not need to dig these, in high mineral, dig - use a test nugget to see
80 to 90% iron probability - The MXT is reasonably sure the target is iron and probably can be ignored
When you are testing a target, be sure you the coil is centered right over it. You may get inaccurate iron probability readings if the coil is not properly centered. This could cause you to loose nuggets.
It also makes sense to use of a test nugget to see how the MXT responds in a particular area highly desirable. Bury a test nugget of about 2 grains size about an inch deep at the site you are testing, and see what the response is. In order to be sure you do not loose the nugget, most people will glue the test nugget to some small plastic piece like a plastic poker chip. Some detector owners have a full set of test nuggets of various sizes that they use.

23) What does the VDI reading in prospecting mode really mean?
The VDI reading is a separate reading from the iron probability output. It is also different from the audio output. The nuggetshooter working with the MXT needs to learn to use all 3 pieces of information. For small nuggets, many give no VDI reading at all - their signal response is so small, the MXT cannot do the analysis needed to calculate a VDI reading. The manual says that small gold nuggets may give a VDI from -20 to +40. Large nuggets may give VDI readings from 40 to 80. Items above 80 on the VDI scale are unlikely to be gold, but still may be well worth digging (hey, even prospectors drop coins once in a while).

24) What is the best coil sweep speed for coins and what is the right speed when hunting gold?
The MXT is not as sensitive as many detectors to the coil sweep speed - which is very beneficial to new users as this is a critical item for many other detectors, but is simply not much of a big deal for the MXT (with one exception - very faint targets such as small gold nuggets and very deep old coins). Because of its quick target response, it works just fine for coin shooting or relic hunting at a wide variety of coil movement speeds. As a result, many folks learn to work their MXT quickly through parks and schools, as it tends to increase their finds. However, this does not hold true when prospecting for gold and very deep old coins- these are two cases where one needs to go slow or nuggets will be missed - especially the smaller ones. Slowing down a bit can also help find the deepest coins near the limit of the detectors ability.

25) Can the VCO pinpoint mode be used to pinpoint gold nuggets?
The VCO pinpoint available by pulling the trigger in coin shooting or relic modes can be used to pinpoint if the gold nugget is large enough. It doesn’t have to be huge, but nuggets below about 1.5 to 2 grains don't respond well to the VCO pinpoint. Excessive iron in the ground can also cause problems, but it sometimes it can be possible to pick out a target even through this type of condition. It is far easier to pinpoint in VCO mode than the regular prospecting mode, and it is easy to flip from one mode to the other and back again, so its worth giving it a try.

26) Can the Relic mode be used to hunt gold nuggets?
Some folks do prospect with the MXT in relic mode as the two tone system is easy to use. You do loose a slight amount of depth, and/or slight sensitivity to small nuggets, but the loss seems to me pretty slight. Getting an ID for iron is fairly reliable in relic mode, but the VDI does not tell any difference between lead or gold - in spite of what the possible target ID might be saying. You can get gold nuggets with the same VDI numbers as you might for lead shot, bullet casings or bullets. The smallest and deepest gold will not produce any VDI score at all (as the max detectable depth is slightly deeper than the depth the ID system will work). It is my opinion that relic mode might be better for prospecting when you are in an area with a very high amount of iron trash, where the ability to actually discriminate out iron would be needed. When using discrimination while prospecting always be sure to set the amount of discrimination very low, or small nuggets can be accidentally eliminated.
One of the things you can do to try to get the best of all worlds is to switch modes. One can hunt in prospect, then when an interesting target is found, switch modes and see what the other modes say about the target before digging. The coin/jewelry and Relic modes also offer VCO pinpointing which is handy if your nugget is large enough to respond to the VCO mode.

27) What about rechargeable batteries?
Although Whites offers a self-contained rechargeable battery system for the MXT, I have been using NiMH batteries since I got my MXT and they work just fine. I get about 20 hours of operation per charge. If you only use your detector once in a while, its probably not worth it to buy the rechargeables, but if you use it at least 5 or 6 hours per week on average, its worth it to get them. If you use your detector often enough, the rechargeables will save you a fair amount of money.

28) I was running my MXT and the screen suddenly went completely blank. What should I do?
A small percentage of MXTs seem to have this problem once in a while. I had this problem intermittently with my MXT, however, after doing it about 25 times over a month or so, it stopped. I did not send it in at that time, and it did not happen even once in several months following. However eventually it started doing this again, so I did finally send it in. It appears to be a contact/connection problem which can be cured by re-seating some of the ICs. It was easily fixed by Whites, and the problem has not reappeared. I would not worry about it if it only happens once in a great while, just turn it off and turn it on again - re-booting the computer system cures the problem. If it happens often, just send it in for repair.

MXT FAQ - Part 1   |    MXT FAQ - Part 2 |   MXT FAQ - Part 3 |   MXT FAQ - Part 4 |   Basic Placer Gold Prospecting   |

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The MXT FAQ and Operation pointers PART 4 (FAQ Questions Nos. 21-28): 21) What should the gain setting be when detecting for gold? One of the main keys to detecting small gold with the MXT is cranking up the gain to the +3 MAX. Having the 6 inch DD is also very worthwhile, both from the stand point that with its small size it is more sensitive to small gold, but also that it allows higher gain settings than the 950 coil under mineralized conditions. It is also less susceptible to changes in soil mineralization than the 950 standard coil. In doing some tests in my yard, I found I could barely detect a 0.5 grain flake with the 950 coil at a gain of +1 (with the flake is right on the surface about 1/2 inch below the coil) - the signal was there but was so weak that in the field, honestly I probably would have ignored it, or not been able to distinguish it from hot rock / background noise. A gain setting of +3 gave a much better response. The 6 inch DD gave a better response to the 0.5 grain nugget at all gain settings. At times, high and variable mineralization may make it necessary to reduce the gain, but when that happens, sensitivity to small gold will be reduced.
22) What does the iron probability reading in prospecting mode really mean? When using the prospecting mode, probably anything that does not make the "grunt" sound (80% iron probability) should be dug. The target ID on the MXT is excellent, however it is not perfect. The ID does not work as deep as the detector will detect. In high iron soil areas, it is possible for small nuggets near the edge of their detection limit to score as high as 70% iron probability. In my experience, most junk iron gives a reliable signal with the special "grunt" sound. However, it you are looking for meteorites, the "grunt" noise may indicate a meteor. Use of a magnet to collect surface iron is also helpful. On the other hand, many small nuggets below about 2 grains weight do not give any ID indication. Tiny bits of iron or lead can also fail to give a VDI or probability response. Repeatable targets which do not give any ID should be investigated. if passing a magnet over the surface does not cause the target to go away by picking up any iron or small hotrocks, the target needs to be dug. The ID will not detect to the deepest and smallest of targets. The key is that if the target is repeatable, the magnet does not remove it, and does not seem to move around as the coil is passed over it, it probably is not iron (it is most likely lead or gold). The iron ID in the prospecting mode should probably be interpreted as follows: 10 to 30% iron probability - The MXT is reasonably sure the target is not iron, dig these for sure. 40 to 60% iron probability - the MXT just can't tell - you will need to dig these targets or you will loose gold. 70% iron probability - in low mineral areas, you may not need to dig these, in high mineral, dig - use a test nugget to see 80 to 90% iron probability - The MXT is reasonably sure the target is iron and probably can be ignored When you are testing a target, be sure you the coil is centered right over it. You may get inaccurate iron probability readings if the coil is not properly centered. This could cause you to loose nuggets. It also makes sense to use of a test nugget to see how the MXT responds in a particular area highly desirable. Bury a test nugget of about 2 grains size about an inch deep at the site you are testing, and see what the response is. In order to be sure you do not loose the nugget, most people will glue the test nugget to some small plastic piece like a plastic poker chip. Some detector owners have a full set of test nuggets of various sizes that they use.
23) What does the VDI reading in prospecting mode really mean? The VDI reading is a separate reading from the iron probability output. It is also different from the audio output. The nuggetshooter working with the MXT needs to learn to use all 3 pieces of information. For small nuggets, many give no VDI reading at all - their signal response is so small, the MXT cannot do the analysis needed to calculate a VDI reading. The manual says that small gold nuggets may give a VDI from -20 to +40. Large nuggets may give VDI readings from 40 to 80. Items above 80 on the VDI scale are unlikely to be gold, but still may be well worth digging (hey, even prospectors drop coins once in a while).
24) What is the best coil sweep speed for coins and what is the right speed when hunting gold? The MXT is not as sensitive as many detectors to the coil sweep speed - which is very beneficial to new users as this is a critical item for many other detectors, but is simply not much of a big deal for the MXT (with one exception - very faint targets such as small gold nuggets and very deep old coins). Because of its quick target response, it works just fine for coin shooting or relic hunting at a wide variety of coil movement speeds. As a result, many folks learn to work their MXT quickly through parks and schools, as it tends to increase their finds. However, this does not hold true when prospecting for gold and very deep old coins- these are two cases where one needs to go slow or nuggets will be missed - especially the smaller ones. Slowing down a bit can also help find the deepest coins near the limit of the detectors ability. 25) Can the VCO pinpoint mode be used to pinpoint gold nuggets? The VCO pinpoint available by pulling the trigger in coin shooting or relic modes can be used to pinpoint if the gold nugget is large enough. It doesn’t have to be huge, but nuggets below about 1.5 to 2 grains don't respond well to the VCO pinpoint. Excessive iron in the ground can also cause problems, but it sometimes it can be possible to pick out a target even through this type of condition. It is far easier to pinpoint in VCO mode than the regular prospecting mode, and it is easy to flip from one mode to the other and back again, so its worth giving it a try.
26) Can the Relic mode be used to hunt gold nuggets? Some folks do prospect with the MXT in relic mode as the two tone system is easy to use. You do loose a slight amount of depth, and/or slight sensitivity to small nuggets, but the loss seems to me pretty slight. Getting an ID for iron is fairly reliable in relic mode, but the VDI does not tell any difference between lead or gold - in spite of what the possible target ID might be saying. You can get gold nuggets with the same VDI numbers as you might for lead shot, bullet casings or bullets. The smallest and deepest gold will not produce any VDI score at all (as the max detectable depth is slightly deeper than the depth the ID system will work). It is my opinion that relic mode might be better for prospecting when you are in an area with a very high amount of iron trash, where the ability to actually discriminate out iron would be needed. When using discrimination while prospecting always be sure to set the amount of discrimination very low, or small nuggets can be accidentally eliminated. One of the things you can do to try to get the best of all worlds is to switch modes. One can hunt in prospect, then when an interesting target is found, switch modes and see what the other modes say about the target before digging. The coin/jewelry and Relic modes also offer VCO pinpointing which is handy if your nugget is large enough to respond to the VCO mode.
27) What about rechargeable batteries? Although Whites offers a self-contained rechargeable battery system for the MXT, I have been using NiMH batteries since I got my MXT and they work just fine. I get about 20 hours of operation per charge. If you only use your detector once in a while, its probably not worth it to buy the rechargeables, but if you use it at least 5 or 6 hours per week on average, its worth it to get them. If you use your detector often enough, the rechargeables will save you a fair amount of money. 28) I was running my MXT and the screen suddenly went completely blank. What should I do? A small percentage of MXTs seem to have this problem once in a while. I had this problem intermittently with my MXT, however, after doing it about 25 times over a month or so, it stopped. I did not send it in at that time, and it did not happen even once in several months following. However eventually it started doing this again, so I did finally send it in. It appears to be a contact/connection problem which can be cured by re-seating some of the ICs. It was easily fixed by Whites, and the problem has not reappeared. I would not worry about it if it only happens once in a great while, just turn it off and turn it on again - re-booting the computer system cures the problem. If it happens often, just send it in for repair.

Nevada Outback Gems
Find out more by checking out All of Our links below:
View our Premium Contemporary Turquoise Jewelry - Wearable Artwork!	View our Unique Gem Quality Turquoise Cabochons
Premium Jewelry, with Gemstones of all types	Top Quality Loose Gemstones - Gemstones of all types
Rare Crystals and Gemstone Rough, all types including Turquoise	Check out our EBAY Auctions of Jewelry, Gemstones and Rough
How to make a purchase, information and terms	More information about us - Nevada Outback Gems
About Nevada Turquoise	Contact us - we want to help
More Info about Turquoise, the Beautiful Gem	Nevada Outback Gems Homepage
Take a virtual tour of our turquoise mines	Our Free Colored Gemstone Information Encyclopedia
Chris' Adventures Prospecting for Gold, Silver, Turquoise and other Gems	Nevada Outback Library and Bookstore - Learn more!
Nevada Outback Gems Website News	More Info about Gem Cutting