Re: Technique needed for distinguishing CaCO3 and bone
Thanks to everyone for your responses. I am very gratified.
Interesting that Gayle should mention dinosaur bone:) While I am not working
with fossils at the moment, I am studying the processes of bone fossilization.
I have in effect made my own fossils through a few different methods which I am
studying to see which method is most effective. As a result, I have several
pieces of bone with varying levels of calcium carbonate coated on the surface
and infiltrating the bone. The bone pieces had been buried in a fine sand
matrix and my initial plan had been to simply measure the level of matrix
agglutination on the bone. This worked, but my advisor has expressed an
interest in quantifying the amount of calcium carbonate that has infiltrated
the spongy bone.
The slices are not imbedded in anything. I was able to get nice slices using a
Beuhler diamond saw without first imbedding the samples.
I have examined the samples using a polarizing microscope. It is true that
calcite polarizes and in some instances fluoresces, but this depends on its
crystalline structure, which is quite variable in calcium carbonate. I can
notice differences between the bone and the calcium carbonate this way, but it
is not plain enough for the image analysis software to detect adequately.
Many thanks for the SEM suggestions. I have examined them using an SEM (without
EDX), but this had a few problems. The machine I was using utilized a
backscatter detection method which was not good for determining differences
between the bone and the calcium carbonate coating very well, nor could it scan
the surface so my field of study was quite limited. The machine was really
designed for taking still photos, not scanning slides. While it works quite
well for its intended use, it had limited capability for my needs.
The machine did not have EDX or microprobe capability. I will have to search
around on campus to see if I can find one that does and which I can use. If I
can't, I appreciate the offer of the folks at CSU and will give you a call. I
am in Fort Collins frequently, so you are conveniently located for me:)
Liz Chlipala gave me a stain to try. We'll see how that works while I am trying
to find a SEM with EDX.
Thanks again for everyone's suggestions and help.
Quoting Gayle Callis :
> 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)
> email: email@example.com
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