Re: Technique needed for distinguishing CaCO3 and bone

From:Philip Oshel

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)

<< Previous Message | Next Message >>