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Fossils
and
How to Etch them


Copyright Dec. 2005
by
Lynn Mills
All rights reserved

Bountiful High, Utah, class of 58.


The fossils
this article is about are from Northern and central Utah. The ability to etch these fossils very from one specimen to another and I have no knowledge of how well fossils from other geographical areas will etch. The fossil bearing rocks from northern and central Utah were limestone or a mixture of limestone and sandstone. I found that rocks containing large amounts of sand mixed in with the limestone were much harder to etch than the pure limestone. The difficulty to etch the limestone was proportionally harder as the sand content increased.

     Watching a fossil slowly emerge from the darkness of a stones interior into the daylight after being hidden for eons is almost a spiritual experience. You are freeing a fossilized animal from its stone walled dungeon where it was imprisoned for perhaps millions of years. Finally they are able to bathe in the light of day for the first time in a long long time. Here is the method I use to etch fossils.

     Lime stone can be dissolved using Muriatic acid, (Hydrochloric acid). This is not to be used by children and of course eye protection is a must. It would be a good idea to keep a concentrated solution of baking soda hand to neutralize any accidental exposures or spills. A set up like the one shown below is ideal. If you don't have access to a burette and if you are handy it is not very difficult to rig  a simple dripper with a funnel, some fish aquarium tubing that tightly fits the small orifice of the funnel and a pair of clamps to control the drip rate.
       

    

Etching Fosils


Some Lime stone samples dissolved faster than others.  By using a burette set up like the one shown on the left it allows you to adjust the drip rate for fast or slow dissolved lime stone. As the lime stone dissolved in one spot you can move the  specimen to selectively dissolve the desired areas to bring out the fossil in the best relief possible. To get the finer details you can use a Q tip dipped into the acid to slowly bring out finer details that would other wise be lost. An average drip rate is about one drop of acid every five seconds.

Be sure to put an acid proof plastic tray under the sample to catch the acid overflow.





Before etching






It just looks like a plain piece of rock but under the surface are dozens of fossil remains waiting to tell their story.. As the Muriatic acid begins to drip ancient animals begin to appear.







After etching






After several hours of etching this is what emerged. The black lime stone etches rapidly but the fossils are dissolved too at a slower rate so care must be taken not to go too far. I am not sure if this is a snail or ammonite. If some one knows please email me. wwindmills@comcast.net








Horn coral

A horn coral is exposed in this etched  sample. These fossils came from a 9,000 foot elevation about twenty miles North East of Logan Utah  yet when these fossils were alive they were living in the bottom of the ocean. This piece of Lime Stone contains snails, Ammonites, gastropods, Crinoids, horn coral and honey comb coral, (not visible in this picture) and unidentified broken bits and pieces. A interesting thing that I have observed is that frequently the fossilized clam shells are tightly closed. To me this indicates a catastrophic event that hopelessly buried the clams alive. Possibly under tons of volcanic ash or pyroclastic flow debris. As you walk the beaches and see clams that have been dead for any length of time they will naturally be wide open. and as the flesh holding the halves together degrades the two halves separate and are scattered. If the fossilization took place over a millennia the halves would have been scattered long before the fossilization process




Knee joint




This fossilized bone was found on private property in the west end of  the Salt Lake Valley on the East face of the Oquirrh Mountains about 5000 feet above sea level. It is a knee joint and was partially encased in Lime Stone. The blue area is where the femur was broken off. The red dot is where the ligament hooked on. The green dot is an entrance for a blood vessel. The yellow is the cartilage area. A person at the museum at the University of Utah was unable to identify it but it is obviously from a vertebrate. Some of the lime Stone was intentionally left on the back side of the fossil and contains fossilized sea shells. I will leave it to you to draw your own conclusions as to what this means.



Jaw bone




The following pictures are not etched samples and are placed just for the readers benefit and enjoyment.

This is a petrified jaw bone with two empty tooth sockets and one tooth still in place. While panning for gold I found it in my gold pan in the Puget Sound area of Washington state.


Iron pyrite shell


This is one of the few fossils I have purchased. It was purchased here in Bremerton, WA. at a rock,  gem and mineral show. It is iron pyrite, fools gold. I have no idea what the process was that formed this or how common Iron Pyrite fossils are.


Trilobite




This is a trilobite My daughter found while we were fossil hunting in Juab County in central Utah. It is  in shale and is not etchable. To find the trilobites you have to split the layers of shale till you find a good specimen.




I hope you enjoyed  the page. I am not an expert on fossils so if you have more information to add or corrections I would enjoy hearing from you.
Email Lynn.

wwindmills@comcast.net
Some of my other pages
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Fishing


Quackery
Cartoons
By
Lynn Mills
Odds and Sods
And a little tongue in cheek

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FishTackler®
Registered TM for sale! Click here for Info.
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1947 - 2007
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