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Prepping Microfossils From The Gulf Coast Eocene


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I have finished my evaluation of two techniques that may be used for the recovery of microfossils from marls and clays such as may be found in the Texas Eocene as well as other Gulf Coast Eocene outcrops. The two techniques evaluated were:

1. The use of Varsol or mineral spirits and hot water to break down the marls and clays, and

2. The use of hydrogen peroxide to break down the marls and clays.

Let me state my conclusion right off since this is easy. I found that the results of both techniques to be essentially identical. Both techniques worked and yielded fossils free of matrix and essentially all matrix material was equally broken down. Also let me say that any highly endurated matrix pieces (Iron oxide concretions for example) were unaffected by either procedure and remained intact. While both procedures were essentially eqivalent in results it is my opinion that the mineral spirits procedure is more amenable to treating larger volumes of fossil matrix, say volumes greater than a gallon. The mineral spirits recovered may be reused in subsequent batches of matrix and the hydrogen peroxide once used is rendered ineffective for subsequent use. Also the hydrogen peroxide produces a foam such that in larger volumes the foam volume may produce an undesirable messy situation.

A word of caution with regards to both techniques. Both procedures present certain hazzards. I recommend that both procedures only be used in well ventilated areas away from any open flames or spark sources. Outdoors is best if you don't have a ventilated hood. Mineral spirits (a paint thinner) is flammable and the hydrogen peroxide is going to break down into water and oxygen gas. While oxygen gas is not flammable, in higher concentrations it REALLY, REALLY accelerates and enhances the burning of other combustible materials.

Both procedures REQUIRE that the matrix materials be completely dry. To accomplish this I dried all matrix materials in an oven at 225F for 48-72 hours. I cannot emphasize this point too much. The matrix materials must be dry! For an oven I used an eletric turkey roaster I bought at a thrift store for $10.00. For some reason my wife would not let me use our kitchen stove for this project.

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Materials used: Mineral spirits - I used Deodorized Mineral Spirits purchased from Home Depot. Varsol is no longer commercially available. I cannot emphasize enough, you must use the deodorized mineral spirits otherwise when the final fossils are recovered they will have a residual odor of the mineral spirits that is unpleasant to some people especially afer prolonged exposure such as working over a microscope picking through a bunch of fossils that smell.

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Hydrogen peroxide - I purchased my hydrogen peroxide, 3%, from the pharmacy at Walmart for $1.00 per quart.

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MINERAL SPIRITS PROCEDURE

I placed about one half gallon of DRIED matrix material in a 5 gal plastic bucket while the matrix material was still hot from the oven. Then I poured the mineral spirits directly on to the matrix material until it was just covered. I let it stand over night to insure it was completely soaked into the matrix.

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Then, using a large funnel with a cotton plug in the bottom I poured the matrix material/mineral spirits mixture into the funnel letting the funnel capture the matrix material in the top and allowing the excess mineral spirits to drain into another container for reuse.

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Once the mineral spirits were drained away from the matrix material the matrix material was placed back into the 5 gallon bucket. Then about 2-3 gallons of boiling hot water was poured into the bucket containing the matrix material. At this point the matrix clods will just disintergrate into a mud. I let it stand until it cools.

After the hot water/matrix material mixture cools then pour it on to a sieve and wash with clean water through the sieve. I used a 25 mesh sieve and a 35 mesh sieve. I have used a sieve made from window screen and even a small kitchen sieve.

After the fossil material is captured on the sieve the material is transferred into a pan and dried at about 225F. Once the material is dried and cooled it is ready for picking and sorting under a microscope.

HYDROGEN PEROXIDE PROCEDURE

In this procedure I placed about a pint of hot matrix material straight from the oven into a quart wide mouthed jar. Then I poured hydrogen peroxide into the jar slowly because of the boiling and foaming action of the liqid as the hydrogen peroxide hit the hot matrix. Stop pouring occasionally and let the foaming subside. Continue pouring until the liqiud level is about 2 inches from the top of the jar. You will note that foam will slowly grow toward the top of the jar. Gently stirring at this point will cause the foam to collaspe. Once you stop stirring the foam will grow again and you will have to stir again. Failure to stir will result in the mixture foaming out of the jar causing a muddy mess.

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The matrix material will immediately start to break down when the hydrogen peroxide contacts it making a muddy mixture. The foaming will slow down afer about 15 minutes. What is happening is that the hydrogen peroxide is absorbed into the matrix and then starts to decompose producing water and oxygen gas. This evolution of gas is what makes the foam.

When the foaming slows down and the matrix material has disintergrated empty the mixture in the jar into your sieve. Wash with clean water. Then transfer the washed material in the sieve into a pan and oven dry at 225F. Once the material is dry it is ready for picking and sorting.

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I cannot attest to the effaciety of these procedures with all matrix materials. It did work with the glauconitic marls of the Texas Cook Mountain and Stone City Formations as well as the Gosport Sand of Alabama and the Cook Mountain of Mississippi.

JKFoam

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an excellent post. the question that crossed my mind while reading it was whether either process affects the long-term stability of the fossils. regular bleach has quite a deleterious effect on things, but i'm not sure about the semi-weak peroxide.

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I agree. First rate information, Jim, and something many members can use.

:goodjob:

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an excellent post. the question that crossed my mind while reading it was whether either process affects the long-term stability of the fossils. regular bleach has quite a deleterious effect on things, but i'm not sure about the semi-weak peroxide.

Tracer,

I have fossils recovered via the mineral spirit procedure over 30 years ago and they show no deteriation. And as to the effects of hydrogen peroxide I cannot say but it is my opinion that on calcitic and aragonitic fossil materials I would be greatly surprized if there were any long term effects. Now if a fossil were pyritized or that other iron sulfide mineral (my mind has gone blank) then I would expect oxidation and resultant deteriation by the hydrogen peroxide.

Also on some of the Cook Mountain fossils vestiges of color markings are preserved in certain fossils. I have not seen any bleaching of this color marking with the H2O2.

JKFoam

Edited by jkfoam
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World-class, JK! Thank you very much for the effort you put into publishing this report :goodjob: ; it is a model for other reports on techniques that I would love to see more of.

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Bullsnake

Great!!! Would this qualify to be pinned?

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Fantastic, Thank You! A very useful and informative post, should be looked upon by anybody who wishes to go micro fossil hunting. Definitely worth pinning! :)

Thanks,

Joe

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Great!!! Would this qualify to be pinned?

Fantastic, Thank You! A very useful and informative post, should be looked upon by anybody who wishes to go micro fossil hunting. Definitely worth pinning! :)

Thanks,

Joe

Done.

These techniques could have wider applications.

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Excellent reprt. As one of the organizers of the annual Fossil Preparation Symposium, I ask you this... would you want to present this to a crowd of interested people at next year's meeting in Seattle? No, we can't pay your way. But think of the fossiling ooportunnities in the Pacific NW. I am already planning a few days of vacation around the conference.

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Excellent reprt. As one of the organizers of the annual Fossil Preparation Symposium, I ask you this... would you want to present this to a crowd of interested people at next year's meeting in Seattle? No, we can't pay your way. But think of the fossiling ooportunnities in the Pacific NW. I am already planning a few days of vacation around the conference.

Sure, I'll consider this. I sent you a PM with some questions.

JKFoam

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I've heard of using Varsol on some of that matrix, but never the exact technique. Thanks for the info.

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Hi,

Thanks jkfoam for this great post.

I use the hydrogen peroxide for more than 10 years to take out the very small teeth of the marl, and I didn't notice degradation. On the other hand, I think that the hydrogen peroxide can affect the pyrite, it is thus necessary to be careful on the fossils which would be in a marl with the pyrite. Furthermore, the hydrogen peroxide produces more foam when there is of the pyrite in the marl.

Does the second method leave an oily aspect on fossils ?

Can the thermal shocks (boiling water and drying in the oven) weake fossils ? I air always either on a radiator (soft heat), or on the sun.

Coco

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CoCo,

I have not noticed any oily residue on any of the fossils recovered by the mineral spirits procedure. I think the hot water followed by a plentiful water wash on the sieve takes care of removing any residual mineral spirits.

As to the aspect of the hot water induced thermal shock damaging any of the fossils I can't accurately comment. Generally, the marls I work with are loaded with shell fragment and shell debris anyway. I use an oven to dry the matrix because some of the matrix clumps are up to 4-6 inches across. The oven speeds things up. There is a danger in too high a temperature. I like to keep the max temperature at 225F to prevent the decomposition of the CaCO3.

JKFoam

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Fossildude19

Jkfoam,

Thanks for posting such an informative guide.

First class work!

Thanks again for your efforts.

Regards,

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Excellent post JKFoam! There are a lot of people that would like to get into micros but have no clue how to extract the tiny fossils from the matrix. I presumed that this method will work in dolostone matrix which harder than heck to break..... thanks for your informative posts!

PL

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Mike from North Queensland

Read your post with great interest as I assume white spirit is a trade name what would you say was the equivelent in Australia shellite or mineral turps?

Neither of these have an odourless verity. Love they way we are divided by a common language.

I googled white spirit and the web page I looked at only confused me more and my suspicion was there comparision was more for there application not for the products chemical structure.

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Read your post with great interest as I assume white spirit is a trade name what would you say was the equivelent in Australia shellite or mineral turps?

Neither of these have an odourless verity. Love they way we are divided by a common language.

I googled white spirit and the web page I looked at only confused me more and my suspicion was there comparision was more for there application not for the products chemical structure.

Mikem

Yes, common language, What a hoot.

I think you are right, mineral tutps, mineral turpintine , white spirits, white oil, mineral spirits, mineral oil, stoddard solvent and etc, are all "equivalent" materials. Do a Google search for "Mineral turps MSDS sheet" and "Mineral spirits MSDS sheet" and compare sections 1,3, and 9. Especially Section 9 which is physical and chemical properties section. Generally they are similiar. They are a little different I think due to the differences in the individual companies refining processes.

If you don't have a low odor version available in Australia you may be able to deodorize it yourself if you are so inclined and have the wherewithall. To deodorize it I would make a slurry of the "spirits with carbon black. After slurrying the mixture allow it to settle and seperate by gravity. Then filer the spirits into a seperate container. Use all due caution because of the flammable/combustible nature of the materials.

Also, you don't have to use low odor mineral spirits inspite of my earlier recommendations. If I did not have low odor mineral spirits then when I was doing the final drying of the sieve washed fossils I would just leave them in the dryer for 24-48 hours longer followed by leaving them spread out on a piece of newsprint in the sunlight for a day or two to help dissipate any residual odor. I hope this helps

JKFoam

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These techniques to a newcomer are essential and very informative and I have logged them into the brain locker for later as I use hydrogen peroxide for almost everything and any odorless products I would use like the thinner has to be this way as I am a artist and have this in my studio.

Thanks

James

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fossilsofnj

Excellent info, I will have to give it a try and my next batch.

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  • 2 months later...

Congratulations on your Hydrogen Peroxide method!

I tried it on some glauconite.

After dessicating the matrix, I poured on the peroxide, stirred, and let it set overnight. BTW, peroxide is $1/liter at Walmart.

My result was that it is probably 95% effective at dissolving the matrix, which is really good!

As you observed, it is amazing how little is left after sieving. 5lbs went to mere ounces.

Thanks for posting.

Steve.

Edited by steve p.
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  • 1 month later...

wow great post, has anyone tried the peroxide method on NJ Marl, specifically Woodbury or Englishtown where Ive been finding a lot of Pyrite, also if I do use the peroxide method on the pyrite "rich" marl would the teeth in the marl be damaged?

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  • 3 months later...
AgrilusHunter

Great post I really enjoyed reading it, and it worked great on some of the shale we have here in Indiana! One note however, the post quoted below states that mineral spirits, mineral oil and white oil are "equivalent materials". While these are all petroleum distillates they are not equivalent. I haven't tried them but I doubt that mineral oil or white oil (which are essentially the same) would produce the same results as mineral spirits. Thanks again for the procedure I'll be picking up some more shale in the next week to try again.

I think you are right, mineral tutps, mineral turpintine , white spirits, white oil, mineral spirits, mineral oil, stoddard solvent and etc, are all "equivalent" materials.

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  • 3 months later...

One thing I've noticed about drying the Stone City Eocene matrix before breaking it down, is that this method seems to harden the invertebrate fossils, so they do not break as easy during the sifting process. I guess it sets them up similar to cement hardening. Once hardened they stay that way. Otherwise, if the matrix is worked wet, some of them tend to turn to mush.

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It is excellent post. I did not know this method of extracting microfossils from clays, I used to work on chalk and coast samples. However, it very helpful to know these information.

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