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  #1  
Old 11-30-2006, 05:13 PM
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Default About Coin Depths

ABOUT COIN DEPTHS

Why are some older coins very shallow when newer coins are deep at the same sites? How can a new coin sink deeper in a few years than an old one in over 80 years?

The Density of Soil

The density of inorganic soil is from 2.6 to 2.8 and any object of greater density, including coins, would eventually sink until the density of the soil equaled the density of the object.

The Sink Rate

The sink rate is determined by the difference in density, the greater the density the faster the sink rate. Contributing factors are vibration, rain, frozen soil, grass buildup, leaves and a few others.

How often the ground gets saturated can be a much bigger driver of coin depth than any minor differences in soil density. Until the ground directly beneath the coin becomes saturated to the point where the dirt becomes suspended in the water, and can move to the sides of the coin due to the coin weight, then little depth due to sinking can occur.

That's why many coins seem to end up in the 6-8 inch range - it takes a real soaker to move them deeper. So maybe the discrepancies in coin depth can be attributed to minor differences in the local drainage. The finer the soil particles, the easier they get suspended and the faster the sink rate.

Chart of Densities

Here is a chart of the densities of some of the common metals we find with metal detectors, also the differences in the density of different metals and a major difference between most of them and soil.

Looking at the chart below, the dime should sink a lot farther than the penny, because the gravity is twice as high on silver as copper is? I know I've found silver just under the grass and then dug 6" or 7" for a clad penny. Nothing worse than getting a deep signal, dig it and it's a clad penny!

The good stuff is sinking faster than the trash. No wonder not many gold coins are being found!

Density of Precious Metals

Platinum 21.45

Gold 19.3

Silver 10.5

Copper 9.0


Densities of Some Common Metals

Aluminum 2.7

Lead 11.4

Magnesium 1.8

Steel 7.8

Tin 7.3

Zinc 7.1

Iron 7.87

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  #2  
Old 11-30-2006, 06:05 PM
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Default Re: ABOUT COIN DEPTHS

That sure is interesting!

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Old 11-30-2006, 06:16 PM
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Default Re: ABOUT COIN DEPTHS

I've often wondered how an IH penny can be 2-3" down, while on the same lot a 1978 Quarter can be 6-8"?

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Old 03-09-2020, 05:41 PM
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Yeah i just started but i agree found quarters from 2001 4 inches down
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Old 11-30-2006, 11:42 PM
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Default Re: ABOUT COIN DEPTHS

This is a favorite topic on the forums. The link below is Monte's opinion. Scroll down, I think his is the fifth or sixth one down the list, and find the post by Monte. Rob


http://forum.treasurenet.com/whites/...ic,4592.0.html

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Old 12-01-2006, 05:30 PM
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Default Re: ABOUT COIN DEPTHS

This info. is very helpful and makes a lot of sense! Thank you!

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Old 12-02-2006, 12:50 AM
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Default Re: ABOUT COIN DEPTHS

Just read Monte's post, and he's right. I have been guilty of that same thing. Not on purpose though. Sometimes I don't take the height of the grass in account. And that fish that got away was T H I S big.

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Old 06-07-2007, 01:59 PM
Richard (Midland) Richard (Midland) is offline
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Default Have you read the Book "Fisher Intelligence" by T. Dankowski?

Originally Posted by Jason View post
Just read Monte's post, and he's right. I have been guilty of that same thing. Not on purpose though. Sometimes I don't take the height of the grass in account. And that fish that got away was T H I S big.
I downloaded two of the older versions free from the Fisher web page. It fascinated me, there was so much information about soil stability, how and why older coins read different, etc., the guy that wrote it is an avid detectorist x 30 yrs, and works at NASA.
HH,
Richard

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Old 06-21-2007, 02:31 AM
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Default Detectordan/MXT

One must also take into consideration such activities as rottotilage or farming.
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Old 07-28-2014, 06:17 AM
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Larger coins barely sink compared to smaller coins i noticed maybe its because the soil has to shift or change more around them i always find them at 1 inch

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Old 07-13-2007, 03:29 PM
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Default Mindreader..

Thats interesting what you say about how things like a bottle cap can sink so far down while something else can be almost right at the top. This makes me think about some of these articals I have read about how SO and SO finds Roman coin buried deep in American soil. Proof that Romans were here before Columbus? I don't think so now, after considering these posts.
RR
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Old 11-18-2007, 06:32 PM
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Certainly coin depths are intriquing-As has been said the water and soil factors are the #1 factors/Mainly water. Find a real wet spot it seems and there deep. Dry spot and there shallow. At our town common if you hunt where the ice hut area is for parking the coins are deep/having found zinc pennies and nickels without corrosion at a true 7" deep with a 11" coil on the machine. I actually cut the plug with a knife which will dig down to say 5"/pop the plug and then nothing but my bare hand digging at the dirt in the hole and 1" at a swipe i scan the handfull of dirt over the coil and repeat if it's deeper. Now like most have said the other coins away from this wet area in the common run about 3-4" max. depth for all coin types.

I always have one of those 3' tapes in my pocket that you can buy for a $1 at wal-mart and measure the deep coins if i happen to remove enough dirt with my hand but can still see the coin in the hole.

Some of the tricks the guys that have been in it for a while use is to move your coil less then 1/2 it's width and sweep again=Stay away from those full coil length swings when your in an area that has a potential for older coins/Even coins on edge or Diamond ring(like i found 2 years ago at a park that had the bejeezum hammered out of it) I barely got the signal and had to sweep the spot a couple of more time so that i could find the exact spot on it as the signal barely came in. Found an Indian head penny in the same park this year at 6 1/2" the same way.

I've found probably 40,000+ coins and 90+% were under 4" deep and the silver is there right along with them if your the first one to hit the lucky spot. About 3 weeks ago when i found the Autori Plebis token it was only 2 1/2" deep and reading in the quarter range but a couple of # lower then a newer Qtr so i really though i had a new quarter to dig up/Much to my surprise i found out different. It was in a high and dry soil. My brother Seated Half Dime that day was the same thing only 3" deep...If i remember right my First colonial was only like 3-4" and doing the same thing on the meter and i though a new Qtr.

Kevin
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Old 07-31-2008, 12:47 PM
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Default Great info

This is great information. The secret is soil density. It can change dramaticly even in the same general area. As stated by many here a gravel road centuries old will have a much greater density than a sandy soil ground. The density of the coin will never change.
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Old 11-15-2008, 05:02 PM
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There's another angle that could have an effect on the depth of coins. Living in New England, we are constantly dealing with a natural movement of the soil in the winter that causes "frost heaves". As I understand this, the hard frost in the winter can make the soil and rocks (and buried coins, I guess) push up toward the surface and that causes the pavement in the winter to become very bumpy in spots. Now, it seems to me that if all this dirt and soil is being pressed upward, then deeply buried coins and other parapenalia would also be pushed upward. This is just my theory and, sometimes I admit, my wife gives me way too much time to think. Steve
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Old 12-13-2008, 08:47 AM
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Even though it's been a couple of years since you posted this thread and I'm
just now reading it,it was very interesting and informative,almost to the point
of scientific I knew that it had to do alot with how wet the ground is and all that but would have never knew all the density's of different metals.
Thanks Carol..HH...Bobby

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Old 12-13-2008, 08:51 AM
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Originally Posted by Steve/WMASS View post
There's another angle that could have an effect on the depth of coins. Living in New England, we are constantly dealing with a natural movement of the soil in the winter that causes "frost heaves". As I understand this, the hard frost in the winter can make the soil and rocks (and buried coins, I guess) push up toward the surface and that causes the pavement in the winter to become very bumpy in spots. Now, it seems to me that if all this dirt and soil is being pressed upward, then deeply buried coins and other parapenalia would also be pushed upward. This is just my theory and, sometimes I admit, my wife gives me way too much time to think. Steve
We also have that alot here in Tennessee during the winter,on real cold mornings when you walk outside the ground has the "ice/frost" crystals pushing upwards out of the ground,sometimes a few inches high.I imagine thats the same thing you are talking about...HH...Bobby

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Old 12-13-2008, 08:56 AM
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OH !! and the point of me even quoting your reply was that i totally agree with the theory of it pushing stuff closer to the surface.I guess my better half
gives me way to much time to think too ...C-ya...HH...Bobby

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Old 03-03-2009, 06:40 AM
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I think the angle of the ground your searching plays a major role as well. We dug up some colonial coppers that were only 3" down, but the trail we dug them on was a hill. Heavy rains wash the layers off the hill, so it never had a chance to go any deeper.Just my guess.
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Old 03-07-2009, 05:28 PM
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One rule of thumb to go by "The most valuable coin will always be one inch deeper than the depth where you stop digging" Steve

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Old 03-23-2009, 03:38 PM
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some of the fields ive detected in where things have been deep have had large cattle tramping over the ground i guess thats sent everything deep
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