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Halo affect on coins.
- Thread starter upnorth
- Start date
You'll find out that if you're a physicist or scientist-there is no halo effect. However, if you're a th'er, there is definitely a halo effect. It seems to be more prevalent in copper, as the elements cause it to leech into the soil better and faster than the more stable silver.
Keeshond John
New member
I believe in the halo affect. Once took a silver dime at a foolish depth of about 9 inches. This with a simple machine that either rang hit or nothing at all. No diminishing sound. I thought how unusual to detect such a coin for I felt I knew my machine and this depth was beyond it. (or so I thought)
At the time I was aware of this "halo affect" and so I conducted an experiment. Placed the dime back to the bottom of the hole and refilled it with the now disturbed dirt. Swung the coil over this spot and did not register a hit. Scraped away about an inch of soil and tried again - nothing. I had to remove about 2.5 solid inches of soil to again sound on that silver dime.
This convinced me old metal of proper makeup does affect the earth around it in time. Minute traces of metal leaching out has to be a real issue.
At the time I was aware of this "halo affect" and so I conducted an experiment. Placed the dime back to the bottom of the hole and refilled it with the now disturbed dirt. Swung the coil over this spot and did not register a hit. Scraped away about an inch of soil and tried again - nothing. I had to remove about 2.5 solid inches of soil to again sound on that silver dime.
This convinced me old metal of proper makeup does affect the earth around it in time. Minute traces of metal leaching out has to be a real issue.
jackinaustin
New member
n/t
I also believe in the effect. I don't know that ALL scientists denie the effect but there
appears to be some denial among some of them.
Most metals oxidize in the air or in the ground, that means they are going to leave
trace elements absorbed by the local ground enviroment. That seems obvious enough to me; the real
test seems to come from those of us who metal detect. Just as was already stated, take a fresh coin
and bury it in the ground and your going to get a different depth reading than if it had been there for a long time.
But what do I know anyway. I could be way off base.
Yea, right.
Katz
appears to be some denial among some of them.
Most metals oxidize in the air or in the ground, that means they are going to leave
trace elements absorbed by the local ground enviroment. That seems obvious enough to me; the real
test seems to come from those of us who metal detect. Just as was already stated, take a fresh coin
and bury it in the ground and your going to get a different depth reading than if it had been there for a long time.
But what do I know anyway. I could be way off base.
Yea, right.
Katz
The picture shows a heavily corroded 1996 zinc penny that I found with the 2500. The 2500 showed the target to be coin size, five inches deep with conductivity of a quarter or 9.5 on the scale. I recovered the penny at five inches. After recovery, air tests of this same penny showed conductivity of 6 or in the gold range. Conductivity air tests of various coins for this machine are as follows:
New zinc penny = 7.5
Copper penny = 8
Clad dime = 8
Silver dime = 8.5
Quarter = 9.5
These numbers indicate that the calibration of the 2500 is right on for the air tests. About all I can say for sure is that coin corrosion and soil conditions in the coin vicinity play a big part in our coin identification process. For most people this is not big news.
New zinc penny = 7.5
Copper penny = 8
Clad dime = 8
Silver dime = 8.5
Quarter = 9.5
These numbers indicate that the calibration of the 2500 is right on for the air tests. About all I can say for sure is that coin corrosion and soil conditions in the coin vicinity play a big part in our coin identification process. For most people this is not big news.
Uncle Willy
New member
Most all coins produce a halo depending on the acidity of the soil. The longer in the ground the larger the halo.
Bill
Bill
Silver coins can have a halo as large as six feet but it would only be detected by Geochemical test
not by a detector; but once it is detected that way it would be eazy to locate with a detector.
A lot depends on the soil and how much water and time there has been to create the needed
halo ( ions released over a long period of time ). Also Geochemical test take a lot of time & $$$
to run if you expect to cover much area. Best not to think to much about it and just go with a
detector as normal.
not by a detector; but once it is detected that way it would be eazy to locate with a detector.
A lot depends on the soil and how much water and time there has been to create the needed
halo ( ions released over a long period of time ). Also Geochemical test take a lot of time & $$$
to run if you expect to cover much area. Best not to think to much about it and just go with a
detector as normal.
Alan Applegate
New member
The halo effect scientists takes about, and the ones detectorists talk about, are two different animals.
All of us know that late-minted pennies are mostly zinc, and heavily plated with copper. Imperfections in the plating expose the zinc to chemicals in the soil, which are primarily alkalis, but can be acidic. As a result, the zinc oxidizes (ZnO). That's the whitish stuff on the surface, usually in the form of nodules. ZnO is almost insoluble in water, but it nonetheless leaches to the surrounding soil. This causes the apparent target size to appear larger; haloing as it were.
Silver is a lot less chemically active than zinc. It doesn't oxidize easily, even in the presents of most acids and alkalis found in soil. Silver oxide, Ag2O, is rather dark brown in color. This is why silver coins which have been buried for a long time, have a dark brown (almost black) hue to them. In any case, any halo effect they produce, is a lot less than that of zinc.
Alan Applegate
All of us know that late-minted pennies are mostly zinc, and heavily plated with copper. Imperfections in the plating expose the zinc to chemicals in the soil, which are primarily alkalis, but can be acidic. As a result, the zinc oxidizes (ZnO). That's the whitish stuff on the surface, usually in the form of nodules. ZnO is almost insoluble in water, but it nonetheless leaches to the surrounding soil. This causes the apparent target size to appear larger; haloing as it were.
Silver is a lot less chemically active than zinc. It doesn't oxidize easily, even in the presents of most acids and alkalis found in soil. Silver oxide, Ag2O, is rather dark brown in color. This is why silver coins which have been buried for a long time, have a dark brown (almost black) hue to them. In any case, any halo effect they produce, is a lot less than that of zinc.
Alan Applegate
Uncle Willy
New member
Also oxygen in the soil which creates the black ( oxidation ) on silver. I wear a belt buckle containing a Morgan silver dollar and I have to clean the oxidation off it every few weeks.
Bill
Bill
Uncle Willy
New member
Without a halo some coins would be passed over as without the halo they would be just out of reach of detection.
Bill
Bill