I found this interesting article and thought some of you might like to see it.
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
thanks to Carol K of south dakota for the article
and here is another good one
AllenB,
"Old Coins" as well as more modern coins, can be located at various depths depending upon the ground environment, the amount of deposition at the site, as well as any other activity that can cause displacement.
I'll add this comment, too. based upon forty-some years of active detecting and encountering many people afield at the time of their discovery of a coin-type target, I am of the opinion that many, perhaps most, hobbyists are not very good at judging the actual depth at which a target was positioned.
Sometimes, they rely on the detector's visual information and a 'coin depth' read-out. This reading can be in error due to the coil used, the control settings used, and especially due to any 'detuning' caused during pinpointing. More often than not, the reading is greater than the actual target depth from the coil.
Those who do not have such a feature also often display an inability to 'guesstimate' the actual, on-site coil-to-target distance. It might be associated with height of the grass combined with the illusion of a hole or cut plus, but many times I have had to correct a claim made afield.
I've heard a guy or gal comment that they just located a 'deep coin' and claimed it to be a good 9 or 10 inches. I'd look in the dug hole at compacted ground, sometimes seeing an impression left by a coin, and show them a few ways to quickly determine a closer depth report.
Take a look at a sheet of your printer paper. Knowing that it is 8
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
thanks to Carol K of south dakota for the article
and here is another good one
AllenB,
"Old Coins" as well as more modern coins, can be located at various depths depending upon the ground environment, the amount of deposition at the site, as well as any other activity that can cause displacement.
I'll add this comment, too. based upon forty-some years of active detecting and encountering many people afield at the time of their discovery of a coin-type target, I am of the opinion that many, perhaps most, hobbyists are not very good at judging the actual depth at which a target was positioned.
Sometimes, they rely on the detector's visual information and a 'coin depth' read-out. This reading can be in error due to the coil used, the control settings used, and especially due to any 'detuning' caused during pinpointing. More often than not, the reading is greater than the actual target depth from the coil.
Those who do not have such a feature also often display an inability to 'guesstimate' the actual, on-site coil-to-target distance. It might be associated with height of the grass combined with the illusion of a hole or cut plus, but many times I have had to correct a claim made afield.
I've heard a guy or gal comment that they just located a 'deep coin' and claimed it to be a good 9 or 10 inches. I'd look in the dug hole at compacted ground, sometimes seeing an impression left by a coin, and show them a few ways to quickly determine a closer depth report.
Take a look at a sheet of your printer paper. Knowing that it is 8
