[Nhcoll-l] Blue/green discolouration of fossils or stoneartifacts

[Rhian Russell]

Hi everyone,

Thanks so much for all your responses!

There's a few things I should have clarified in my question, my apologies:

We did send some samples to CCI for investigation, and their report suggested that the discoloration was in fact a stain produced by a reaction between volatiles offgassed by some plastic or rubber, possibly a mold or cast that was stored in the cabinet.

They determined that the cause was not vivianite, baricite or any other blue mineral; nor was it caused by any adhesive on the fossils including Paleobond or a cyanoacrylate activator; or hydrogen peroxide, MEK polyester catalyst or HCl vapour/liquid.

At this point I'm mostly interested in finding out how common an occurrence this is - and judging from the responses so far there isn't an epidemic of fossils turning green all over the place, at least not due to exposure to plastics or rubbers.

Cheers,

Rhian

________________________________________
From: nhcoll-l-bounces at mailman.yale.edu [nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Rhian Russell [rhian.russell at gov.ab.ca]
Sent: Wednesday, October 10, 2012 5:38 PM
To: nhcoll-l at mailman.yale.edu
Subject: [Nhcoll-l] Blue/green discolouration of fossils or stone artifacts

Hello all,

We have encountered a phenomenon in our fossil collections where a few specimens have developed a blue/green discolouration, either on the surface of the fossil itself or in the surrounding rock. I've just read a paper describing the same thing happening to flints at the Natural History Museum in Verona (Tapparo et al., 2011, "The mystery of the discoloured flints. New molecules turn prehistoric lithic artifacts blue" in Journal of Analytical and Bioanalytical Chemistry Vol 399 (7) pp.2389 - 2393).

Basically, it seems that volatiles from certain plastics and/or rubbers react to cause the formation of a blue or green stain on the surface of the object and its surrounding matrix.

I'm wondering if anybody has seen this occur in other collections? It requires a very particular set of circumstances so I'm assuming it would be quite rare?

Cheers,

Rhian Russell
Conservation Technician
Royal Tyrrell Museum of Palaeontology,
Box 7500, Drumheller, Alberta T0J 0Y0
Phone: (403) 823 7707 Ext. 3306
E-mail: rhian.russell at gov.ab.ca<mailto:rhian.russell at gov.ab.ca>

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