Jump to content
Joe D.

Factors Affecting Coin Sink Rates

Recommended Posts

EDITOR'S NOTE: This thread split off from a prior subject on coin detecting here.


I asked someone very knowledgeable about soils and how objects move in and on them! About the "sinking of coins" subject several years ago! And got a very detailed answer!

In a nutshell, coins and other object don't actually "sink" in normal soils:

*  They can be compressed deeper by natural, or man made forces! (Examples: Foot and/or vehicle traffic; Animal traffic!)

*  Soils and organic materials build up over time! Or are added by humans, or short term natural events! (Examples: Mowing; Plowing; Natural decomposition of organic plant and animal matter; Wind blown soils; Flooding; Land slides; Etc...)

*   Ground conditions can very greatly and affect the depth the coins were originally dropped! (Example: An uneven or rocky area that may have been a gathering area before being filled and leveled for a playing field!)

*  Seismic activity, and/ or liquefaction of soils buy various natural and manmade events!

   And there can be multiple, and combined events over a short, or long period of time!

This is by no means comprehensive, and i did not even cover beach conditions and the effects of waves, tides, and currents on coins and other objects,  and their shape and weight factors!🤯🤯

And this was the Short answer!🤣






Share this post

Link to post
Share on other sites

A process known as Bioturbation is a very significant factor in coin sink. Essentially, earthworms disturb the soil around the item, until one dry/wet/cold/whatever day, the conditions allow it to drop 2 or 3 mm. Repeat this for 100 years and your target is 20cm ( 8 inches) down. If the ground is inhospitable to worms, the sink is much slower.

Unfortunately for us, earthworms tend to live in the top 30cm ( 12" ) of soil, because that's where the plant matter they eat is located.

  • Like 4

Share this post

Link to post
Share on other sites


 That's funny you mention the earthworms! That subject was the original source of my "coin sink" question!  I just didn't mention it in the previous post! 

I have a small park near me that was once part of an old graveyard! (Graves removed long ago) It has several very large trees that constantly shed leaves, and the soil is very rich and loamy with tons of earthworms! In this situation its a combination of the leaf breakdown, mulcher mowing, and finally the earthworms that are processing the leaves and grass clippings,  and burying anything that falls on the ground here! To complicate matters, there are large power lines overhead, and a constant homeless element that litters the park with all manner of aluminum trash!  

I would call it more of a coin burying, than a coin sinking! But it could be called either one i would guess! I was formerly a sinking advocate until i conversed with the person i referenced above! Now i'm in the burying camp!👍👍

  • Like 1

Share this post

Link to post
Share on other sites

That's not an earthworm, it's a confused snake! crikey!

  • Like 2

Share this post

Link to post
Share on other sites
22 hours ago, geof_junk said:


That reminds me to get my dogs heart worm pills, I would hate to see something like that come out of him.

The poor guy would die from just 1 of those!

  • Like 1

Share this post

Link to post
Share on other sites

Interesting article, but I like the pixie dust theory the best.

The pixie dust theory simply suggests that one can find almost anything if they are in the right place at the right time with the right equipment and a good luck charm.

I believe that you have some science on your side, but I still have a wild imagination of things, so I vote pixie dust.

  • Like 1

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By Hardtimehermit
      Out waging the new wond around Reno, and finding out what the Equinox 800 is like. Thanks to so many of you veterans and just plain smart people my early days swinging the nox have been a pleasure. Here are some of my finds in my first two weeks. 

    • By GB_Amateur
      I've found the winter / New Year period a good time to reflect on the past and hope for the future, and that applies to my detecting as well.  Since I keep a log of finds (coins and jewelry) by year I can compare that part of detecting with the recent (starting in 2017) past.  Unlike previously, 2019 came up short in every meaningful quantified category:  total collectible coins, total Wheat pennies, total $-value of common coins, total days hunted, total hours hunted, average hours/hunt.
      The causes are many:  fewer permissions, fewer previously hunted parks & schools, very dry late summer / early autumn, less stamina with age(?).  Ironically all that on top of the fact that I had more free time since my work load was reduced more than half.  All of this needs to be addressed for 2020.
      In terms of gold hunting, as chronicled here I quadrupled (2 to 8 😁) my lifetime native gold finds with about the same number of hours/trips West, but that is almost completely due to the benevolence of a friend who took me to one of his gold producing sites and added some instruction along the way.  I'll be on my own in 2020 which means "research, research, research!"
      There are other valuable takeaways besides simply counting finds, though.  Knowledge is a big one, and required by me.  So what did I learn last year?  The biggest increase in knowledge was finally learning to listen to the quality of tones from the Minelab Equinox 800.  Along the way I went from a love/hate (exaggerated description of course) relationship to one of trust.  But that really didn't happen until the very end of the year.  You may recall I wrote a long, sad(?) post in August about a frustrating hunt of an 1850's homestead when I was driven bonkers by EMI.  That was in the heart of the dry season when not only do we lose depth due to the dry soil, but also (in good conscience) have to give up digging in public sites because of the inability of the grass/sod to heal itself.  I was at an all time low.  I can thank many of you for helping me make an attitude adjustment.
      One of the problems I had previously with trying to listen and learn sound/tone quality was that I just couldn't force myself to listen to '50 tones'.  What I realized is that you can get a big boost from listening to the quality of tones in 5 tone mode.  Another surprising occurrence which I can't explain is that EMI became much less of a problem.  I used to run gain of 20 max due to EMI, dropping to gain of 15 in some cases, and even being more/less forced to switch to single frequency mode (and never 5 kHz where the EMI was worst) if I was still getting bad EMI at gain of 15.  The last several hunts I was able to run quietly at gain of 22 consistently, including in a local park where I typically had to switch to single freq.  Yes, it could be temporal/seasonal variations in EMI but I don't think so.   I've hunted that particular park year round, morning through afternoon, weekdays and weekends.  Maybe the source of EMI was removed, but that doesn't explain my experiences at other locations which also gave EMI problems in the past, but not now.  I don't think it's the recovery speed (I've been running exclusively at 5), or mode (consistently Park 1).  However, I do wonder about the 2.0 software upgrade.  My loss of EMI problems has occurred since then although I don't recall it being like a switch being thrown.  I've been hunting Iron Bias F2=5 most of the time since I loaded that upgrade in software.  Is it possible ML made other changes which lessened EMI?  And, again, it may not have anything to do with the detector.  Unfortunately I haven't gotten a chance to return to that 1850's homestead give that really bad EMI a test.

      I haven't posted a finds photo lately.  Shown above are the highlights of my last 4 hunts of 2019 (all after Christmas) and first 3 of 2020.  I found a silver coin in 6 of those 7 hunts.  The dolphin ring is sterling and note it isn't a closed ring (dolphins not touching) but still came up with a TID just above Zincoln (i.e. it was about 22 on the Eqx).  The bronze token is from a local (Southern Indiana) intercity bus lines which was in business from the 1920's through mid-60's.  The two items on the left are shown to emphasize the unmasking ability of the Eqx.  That large iron loop (have no idea what it is) was about 4 inches laterally and a couple inches deeper than one of the Mercs, which itself was 6 inches deep.  In another case, the wing nut (non-ferrous TID, but I don't know it's composition) was close to the surface.  I think it ID'ed in the pulltab zone and I dug it specifically to see if it was masking anything.  Six inches laterally and 8 inches deep was another Merc.  I don't know if the Eqx probably would have unmasked that (my guess is 'no') but it does show that removing undesirable targets will pay dividends.  That Merc and one of the others are the deepest dimes I've ever recovered.  None of the coins (including the Wheaties) are valuable date+MM.
      A few final points -- Steve H's online interview by Dick Stout prompted me to reread Coinhunting... In Depth.  A couple things jumped out from that book.  (I'm paraphrasing / reworking but I give him credit for these concepts, at least):  1) Why are you wasting your time returning to the same places you've hunted to death?  2) When you go out detecting, spend some time beforehand considering your goals; then keep them in mind during the hunt.  Thanks, Dick!  Those plus a few other things yet TBD are going to make 2020 my best year ever.
    • By Steve Herschbach
      This is something you do not see very often, a $1 gold coin found metal detecting. A lot of traditional coin hunters would pass on something like this because it gets identified more as trash (it reads as foil) than a coin. Lots of $1 gold coins were lost but few are ever found. A good example of what digging all non-ferrous targets can accomplish in the right locations. Great find, one I would be thrilled to make. Link deleted since Findmall Forum update broke all old links
    • By steveg
      Hi all!
      It was a beautiful day here on Monday -- and my buddy and I got out for some digging. We hit a park that I had never hunted before, but he's been there several times over the years. As all of our city parks are, it's been well hunted, but after a couple of hours I lucked into a little "hot spot." It was a very small area, as it turns out -- maybe 30' x 30' maximum -- but I started hitting deep coins. Each one was at least 7" deep, but most of them were Garrett Pro-Pointer deep (8" to 9"), the deepest pushing 10". My guess is that for whatever reason, the coins ended up deeper than normal in this little area (I know a layer of sod had been installed here, as I was cutting through that plastic "mesh" underneath the grass layer), and that they ended up just deep enough that they were missed by most other hunters/other machines.
      Whatever the case, it's always nice to get into a little area that gives up coins like that; after I had hit several coins (enough to convince me there was something going on there) I called my buddy over to join in on the paydirt. All told, we managed 14 old coins from this tiny little area, plus a few buttons and other interesting items. It's been quite awhile since I've hit a little "hot spot" that was that productive, in a public spot...
      Here are my digs; I got several of these as "live digs" on video, so I may try to piece together a video (if I can give myself a crash course, and learn how to edit well enough)!
      (The Mercs are 1935-D, 1942, 1944, and 1945; the Rosie is 1959; the Wheats are 1920-D, 1937-D, 1941, and 1946, and the Buffalo is 1937).
      Thanks, all!

    • By Againstmywill
      I tend to save all my finds and put them on a tray until I have time to sort them. Last year it seemed like I had too little time to sort because the two trays hold a whole year's worth of junk, jewelry, and coins. I did have additional plastic bags partially filled so the trays wouldn't overflow too much. The box holds the change that came out of all that junk on the trays. There are no picks of the jewelry because I remove that as I come home after detecting. Just wanted to share with others new to the hobby so they know that there will be junk as well as awesome finds. I used to keep track of how much change I found on each hunt, but now I just take it in and cash it out for Amazon credit. So, I'm not sure how much the change is worth yet because I have yet to take it in.

    • By Denny
      Detected a  stretch of  a river that had  some erosion on the banks and sand removed down to the gravels.  I dug up many coins including a buffalo nickel and a silver dime that someone was going to make into  a ring. The best find was a 14k ladies ring 3.1g  (not a genuine stone).   Also dug up what looked like a white gold  ring turned out to be stainless steel.     
      The tarsacci has good recovery speed like the T2 worked great in  the trashy area  with  broken pieces of  rusted old steel cans, bottles caps, bits and pieces of iron along with all the newer junk tossed into the river.   The tarsacci worked better than my T2 it found targets in a area I couldn’t use the T2. 
      The 2 wheat pennies were dug up  at a old park 6-7 inches deep.   The tarsacci  goes deeper it’s just that  my ctx did a good job sniffing out most of the oldies at this old park.

  • Create New...