[Nhcoll-l] [External] Blue Matrices

[Tacker, Christopher]

Hi, Katie,


This is what EDA was made for. The machine you need is an SEM with EDA (Energy Dispersive Analysis). That will give you a spectrum that identifies the elements present in the blue stain. In particular, you need an Environmental SEM. These use a partial pressure of nitrogen in place of carbon coating the specimen. Obviously for these fossils, you don't want to carbon coat them.


I would start with the shards that don't have fossils. 15 kV is a good place to start for accelerating voltage. That covers the excitation energy for most of the periodic chart. With this color blue, I suspect that copper is involved. But there are so many different transition metals that could contribute, you really need to measure and not guess.


Once you have a chemical analysis, then you can start to investigate proper means to curate the material.


Feel free to contact me to discuss it if you like.


Cheers,

Chris


Chris Tacker, Ph.D., P.G., Research Curator, Geology
North Carolina Museum of Natural Sciences       http://www.naturalsciences.org/
11 West Jones Street
Raleigh, NC  27601-1029

Please note:
E-mail and phone have both changed:
christopher.tacker at naturalsciences.org     919-707-9941.

E-mail correspondence to and from this address may be subject to the North
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Subject: [External] [Nhcoll-l] Blue Matrices

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Recently the museum I work at received a donation of fossils with matrices that have turned blue . The donor has said that they were stored in a dark, dry basement in paper towel/plain newsprint and were not treated with anything. Some of it looks like accretion while some of it appears to be the matrix itself and they do not fluoresce under short or long wave UV light.

Has anyone seen this before or know what may have caused it?

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