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I went back to my very productive Devonian Martin Formation and Mississippian Escabrosa Formation near Superior, Arizona to retrieve my large single crinoid head fossil. 

 

Amazing Arizona Adventure original post link

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After some acid prep four crinoids and one blastoid were clustered together. Currents probably sorted them by size and shape. 

9B86642D-558D-4B34-8E93-0B148C69EB48.jpeg

 

Several more hours of acid prep made the remaining four best ones stand out. I had to carefully break away pieces of shell that adhered and covered the crinoids and blastoid. Careful monitoring of their progress prevented any of them falling off the matrix.

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The resulting piece is probably the finest crinoid and blastoid assemblage ever found in Arizona. Finding one crinoid or blastoid cast in Arizona is very hard let alone four or five together. The two largest crinoids in the center and left are likely Physetocrinus lobatus. The upper right is an Orophocrinus saltensis blastoid. The lower right is an unknown crinoid. (Any idea what it is?) The field of view is about 7.5 cm wide.

 

Keep looking for updates as I prep and post more fossils. I found several loose crinoid heads.

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Manticocerasman

nice, what kind of acid do you use on them?

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2 minutes ago, Manticocerasman said:

nice, what kind of acid do you use on them?

Muriatic AKA HCl acid. The people at the hardware store must think that I have a really large pool with all the acid that I buy from them. 

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3 minutes ago, doushantuo said:

be careful with the acid

don't drop it

I never drop it. When I spill it I always have lots of water nearby to dilute it.

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Congrats on that unique find. Are the fossils silicified?

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Awesome find and fantastic prep work.  Do you neutralize the Muriatic acid on the fossil with a liquid solution of baking soda and then rinse thoroughly or just rinse? 

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What exquisite echinoderms!!!  Congratulations on the awesome find and well done on the prep!

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1 hour ago, Ludwigia said:

Congrats on that unique find. Are the fossils silicified?

Yes.

1 hour ago, Ruger9a said:

Awesome find and fantastic prep work.  Do you neutralize the Muriatic acid on the fossil with a liquid solution of baking soda and then rinse thoroughly or just rinse? 

I just soak in fresh water for a period at least twice as long as it was in the acid changing the water a couple of times. Often the acid solution has been neutralized by the limestone when I take the fossil out. Soaking in water gets rid of the salt, calcium chloride. Insufficient soaking produces fossils that grow lots of needle like crystals.

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35 minutes ago, DPS Ammonite said:

Yes.

I just soak in fresh water for a period at least twice as long as it was in the acid changing the water a couple of times. Often the acid solution has been neutralized by the limestone when I take the fossil out. Soaking in water gets rid of the salt, calcium chloride. Insufficient soaking produces fossils that grow lots of needle like crystals.

Thanks!

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How much do you dilute the acid?  HCL is pretty harsh compared to acetic or formic acid, unless it is diluted a lot.

 

Don

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Very cool looking Crinoids. Some of the detail is very nice too. 

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7 minutes ago, FossilDAWG said:

How much do you dilute the acid?  HCL is pretty harsh compared to acetic or formic acid, unless it is diluted a lot.

 

Don

Starting with a 29% solution, I dilute it to a 10-20% solution. If the fossil is fragile, I use a lower concentration of acid to prevent concussion fracturing from the bubbles forming and popping. The biggest problem with the higher concentration solutions is from overtopping the container from the vigorous bubbles and organic slime from the limestone.

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Very nice prep work and awesome find, John!

Thanks for posting it!

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