Written by the Treasure Guide for the exclusive use of the Treasure Beaches Report.
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| One Ounce Gold American Eagle Coin Used In Metal Detector Tests. |
As you probably know, I've been conducting some metal detector tests with a variety of coins. I've been looking at the metal detector's ability to identify those coins, and have also been looking at the depth of detection in a very general way. I've taken notice of the depth at which the coins can be detected but did not attempt to take precise depth measurements due to the nature of the tests. I expect to take more precise measurements of detection depth at some later time.
For my most recent tests, I used s 1922 Peace dollar, and a 1971 Kennedy half dollar, which I used in some earlier tests, but for this test I added a 1998 one oz. gold American Eagle coin. This test was conducted at the same test site as the previous tests.
The American Eagle coin is 91.67% gold, 3% silver, with the remainder being copper with a reeded edge. It is 1.287 inches (32.70 mm) in diameter, contains one gold troy ounce and weighs 1.0909 troy ounces (33.931 g). So in diameter the gold coin is a little smaller than the Peace dollar but bigger than the clad Kennedy half.The Equinox 600 produced conductivity numbers mostly in the range of 32 -34 on the Kennedy Half, and 37 - 38 on the Peace dollar. Those numbers are consistent with those found during the previous tests. The American Eagle gold coin produced numbers that centered on 26 - 28. You may recall that the conductivity numbers are more consistent when the detection depth when the depth was moderate. When depth is near maximum, the Equinox produces less consistent conductivity numbers.
Depth numbers will be more meaningful when tests are conducted on the beach on buried coins, so I didn't attempt to be real precise on depth measurements during these tests.
When the coil was close enough to the coins, the conductivity numbers obtained on these three coins was sufficiently different enough and consistent enough to reliably discriminate between the three coins used in this test. Once again, when the coil is near maximum detection depth, you cannot rely on the conductivity numbers to be accurate. Under those circumstances some numbers will be way off.
It seemed the one oz. American Eagle was generally detected at a slightly greater depth than the other coins used in this test. People will generally use the Equinox multi-frequency setting when using the Equinox, and it produced the best results. Varying the frequency setting did affect depth, and in some very significantly. Some frequencies really reduced depth on these coins. I'll have to look at that more precisely some other time. It seemed the gold coin actually got at least an extra inch on the other coins at times. I wasn't expecting that.
In this test, I appeared that the Equinox conductivity numbers fairly accurately reflected the relative conductivity of the metallic composition of the coins. Having found in previous tests that the silver coins produced numbers that were very similar to the copper/nickel clad coins used in previous tests, the close relationship between the Equinox conductivity numbers and the relative conductivity of the predominate metals used in the coins surprised me.
Below is a short list of relative conductivity for some of the most predominant metals.
My previous tests on silver and clad (mostly copper/nickel) coins showed little discernable difference in the Equinox conductivity numbers for coins of similar size. When silver halves were compared to clad halves and silver dollars to clad dollars the coins of similar size but different compositions were very similar.
In this test, the silver Peace dollar conductivity numbers were a few points higher than the clad Kennedy half - enough to tell the difference when the coins were not too distant from the coil.
From the above table, you'll see that gold has a conductivity that is close to 70% of silver. In this test, the Equinox numbers for the silver and gold coins reflected that surprisingly well (37/27 = 73%). The After the previous tests, I was amazed to learn how accurately the Equinox conductivity numbers reflected the relative conductivity numbers for the predominant metals, despite the fact that the coins included other alloys. It seems that the conductivity of the copper/nickel alloy coins aren't very different from the silver alloy coins. That must explain the failure to reliably discriminate between the silver and clad coins of similar size and type.
I quickly checked the same coins with the Garrett Ace metal detector. The detection depth obtained by the Ace was much less than that obtained by the Equinox. The Ace reliably identified the half-dollar and dollar coins used in the previous tests remarkable well, however, the one oz. American Eagle gold coin identified on the Ace meter as a dime. While the Ace did a great job of identifying common coins, there was no place of the target ID meter for a one oz. American Eagle gold coin and the Ace target ID was very misleading for that coin.
For this test, my biggest takeaway is the accuracy of te Equinox relative conductivity numbers. I was beginning to doubt that, but it now looks like the earlier failure to reliably discriminate between the silver and clad coins used in the previous tests was due to the fact that the difference in conductivity of the metallic composition of those coins was actually very small.
I was also surprised that the Equinox seemed to get greater depth on the gold coin. I didn't attempt to measure that precisely in this test, though, so that remains to be verified in future. I plan to look at that more closely in the future.
Thirdly, don't expect the Ace to identify gold coins for you. The ID meter was rock solid on common coins, but the gold coin was completely misidentified.
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The surf is not big today, and the tides are pretty flat. The wind is coming out of the south.
I'll have more tests in the future, but also have some great new finds to post.
Good hunting,
TreasureGuide@comcast.net