Re: Technique needed for distinguishing CaCO3 and bone

From:Gayle Callis

Hi Phil,

I did not vacuum the PMMA since the danger was pulling the delicate,
ancient 60 million year bone into pieces, the bone just sat in the PMMA
embedding mixture (the one we use is NOT super thick, so it infiltrates
perfectly.). I had one person tell me PMMA would never work with T rex bone
or other dinosaur bones,  Well, that was a challenge I could not resist, so
I WON! and had wonderful sections of T rex tibial bones that never crumbled
into nothing with diamond cutoff blades on Buehler Isomet.  

It is not that the bone is replaced by the CaCO3, but coated with it.
Archeologists have found bones inside ancient caves and the bones are
intact (skulls, etc) but coated by the constant dripping of water from cave
ceiling (the coating becomes CaCO3, correct?) turning the bones into bone
stalagmites or tites, which is on top or bottom here. That is what I
thought he meant per this statement made "I have several slices of bone
with calcium carbonate deposited on them". 

  At 03:11 PM 7/2/2003 -0500, you wrote:
>CaCO3 is birefringent, at least in some crystal forms. Calcite is a 
>classic example.
>But fossils ... the CaCO3 could form pseudomorphs, where the crystal 
>morphology takes on the form of whatever it replaced.
>Did you have to do any vacuum steps to get the PMMA completely into the bone?
>But ... fossil bone is not necessarily CaCO3. Our lab did T. rex also 
>a few years ago, and the bone had not been replaced -- it was still 
>apatite. An appropriate mineral for T. rex.
>>Enlighten us please!  Are you working with dinosaur bone?  Is it embedded
>>in anything?  Why is there calcium carbonate covering the bone?  Is this
>>from being a cave with water dripping on bones for a long period of time,
>>like thousands of years, encasing the bone with CaCO3?  like a stalagtite?
>>I know that dinosaur bone can be embedded in PMMA, even in its extremely
>>dried state.  I did T rex bone that had laid around for many millions of
>>years, did no do any dehydration or anything to disrupt the fragile bone
>>(trabeculae were amazing lifelike and intact).  The bone was infiltrated
>>ONLY with PMMA embedding mixture, then allowed to polymerize.  After that,
>>one could cut it with a diamond blade without any problems and no ancient
>>(extinct) bone damage.
>>If you can stabilize the bone/CaCO3 in plastic, you should be able to slice
>>it thinnly (200 um or more) then do image analysis) - the bone, even
>>extinct bone could possibly be surface stained to distinguish it from the
>>CaCO3 within the slice.  You could also examine the bone with polarized
>>light, I don't think CaCO3 polarizes, but not sure on this, some salt
>>crystals will polarize or you could distinguish the salt crystals from bone
>>collagen matrix by differences between collagen and crystal - i.e. the
>>morphology, if you will.  Hmm not sure I said that correctly.
>>Just some thoughts.
>>At 07:13 AM 7/2/2003 -0600, you wrote:
>>>I have several slices of bone with calcium carbonate deposited on them.
I am
>>>searching for a good way to readily distinguish between the original bone
>>>the deposited calcium carbonate. I can usually do so by visual inspection,
>>>the differences are too subtle for my image analysis software to pick
up. My
>>>goal is to be able to quantitatively determine the amount of deposition on
>>>bone. If someone knows a stain or some treatment that I might be able to do
>>>that will help bring out the differences between the calcium carbonate and
>>>bone, I will be most appreciative.
>>>Thanks for your help.
>>>Joe Daniel
>>>Grad student
>>>Museum and Field studies Program
>>>University of Colorado at Boulder
>>Gayle Callis
>>Research Histopathology Supervisor
>>Veterinary Molecular Biology - Marsh Lab
>>Montana State University - Bozeman
>>S. 19th and Lincoln St
>>Bozeman MT 59717-3610
>>406 994-6367 (lab with voice mail)
>>406 994-4303 (FAX)
>Philip Oshel
>Supervisor, BBPIC microscopy facility
>Department of Animal Sciences
>University of Wisconsin
>1675 Observatory Drive
>Madison,  WI  53706 - 1284
>voice: (608) 263-4162
>fax: (608) 262-5157 (dept. fax)
Gayle Callis
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)


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