ABOUT COIN DEPTHS

[Carol K]

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

 

[spittfire]

That sure is interesting!

 

[Jason]

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"?

 

[rcasi44]

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/index.php/topic,4592.0.html

 

[b-boop]

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

 

[Jason]

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.

 

[rcasi44]

As you see he doesn't think they actually sink. Rob

 

[JimInPhilly]

I think mass , shape and angle also play a role in the sink rate.

Jim

 

[spittfire]

Most of my older coins have been shallower than the junk coins. It makes sense when you read that article.

 

[Florida Tabdigger]

Most old coins I find are less than 5 inches. I have always contributed the "sinking" to wet soil and thunder vibrations along with deposition.

 

[seadog2]

Most of my silver coins have been found around large old trees at very very shallow depths. I think the roots prevent them from sinking.

 

[dooby]

That was way to interesting !!! I have always wondered as well why I find very few coins at a depth greater than 3 inches. I also have found that if my display reads 4 inches deep I find the coin at half that depth............

 

[Hrsetrder]

I have found that most good (silver) coins are found at depths of 4" or less. I have found silver halfs just under the grass at less than an inch. Found dimes at 4-8" , so size does not always matter when it comes to the rate it sinks. Note the half was a 1942 and the dime was a 1961 at 4"+ . You would think that the half being larger , heavier and older would have been deeper. Of course most people already know that in order to maximize silver finds is to hunt private properties ( with permission of course) . These sites are normally virgin sites and have not been hunted. Parks and schools in most areas have been hammered hard and finding silver is slim to none . Every private homesite I hunt always yeilds silver coins ( if it is an old enough site) .
HH , David

 

[brooklynct2003]

I've often thought the same thing about coin depths. The density of the coin I believe plays a major part. Seems like I find alot more zinc pennies these days than copper ones, considering they are 30% lighter but occupying the same mass.

One must also consider the environment.... water table levels, erosion factor, density of the soil, obstructions like roots, rocks etc that hinder the coin from sinking. A well travelled gravel path will have much denser soil than loosely packed loam just a few feet away. Human and animal activities above the soil like sports activities, farming plows, raking, landscaping, can also change the coins depth up or down even after many years in the soil.

Still perplexes me at times though. I find zinc pennies sometimes 4" down, yet the 2 silver coins I found(a 1918 half dollar and a 1903 dime) were both found within 1" of the surface.

Gil from CT

 

[chopz54]

Dont think anyone has mentioned one of the main contributors to " sinking "

WORMS. MOLES. Etc They are constantly changeing the

underground strata and angle of objects.

Chop

 

[MattInPhila]

Coin Depths

Excellent info! Thanks. I`ve been curious about why some coins are shallow and others quite deep.

 

[terry]

Hi I found a 1943 U S cent about an inch from a silver 2 Bavarian Mark coin 1876, the coins were found in parkland in the Wales U.K. I assumed that the Bavarian coin was brought over from Germany during the war as a war momento, they were at the same deapth, can anyone shed some light on Why they were found togeather when the cent is small and the Bavarian coin is twice the size,

Terry

 

[minereader]

Good info!

I hunted a Female College(went defunct in 1936) back in the 80's, and mopped up. Alot of silver, Indian heads, rings, etc. It was a MDer's dream. Went back recently to hunt the real "trashy" areas that I left way back then. It is amazing the junk that has worked down deep into the soil since the 80's. Seems a crushed pepsi can will go awful deep, along with clumps of foil. I actually dug a golf ball that was deep, near a junk target. Dug about a pound of trash, with no very good targets. Of course, it was still fun. Thanks for the info, Carol!

 

[Richard (Midland)]

Have you read the Book "Fisher Intelligence" by T. Dankowski?

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

 

[FXDiz]

Hi I found a 1943 U S cent about an inch from a silver 2 Bavarian Mark coin 1876, the coins were found in parkland in the Wales U.K. I assumed that the Bavarian coin was brought over from Germany during the war as a war momento, they were at the same deapth, can anyone shed some light on Why they were found togeather when the cent is small and the Bavarian coin is twice the size,

Terry

I have to ask about the 1943 US penny. Is it a steel or copper penny. The copper one's are VERY rare and worth mucho bucks. See this site: http://acoins.com/1943penny.html