alfredo
Site Admin
Joined: 30 Jan 2008
Posts: 981
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 Posted: Nov 30, 2010 19:35 Post subject: Re: Amber |
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| Those who want to define true amber as only coming from the Baltic, excluding fossil polymerized resins from elsewhere, are just like the folk who tried to define emerald as only being colored by chromium, excluding those colored by vanadium. It's not science - It's commercialism, an attempt to exclude the commercial competitors. |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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| Posted: Jan 25, 2011 14:56 Post subject: Re: Amber |
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| Pete Modreski wrote: | | Elise wrote: | I just came in from a trip to meet Maggie Campbell Pedersen, author of one of my favorite reference texts: Gem and Ornamental Materials of Organic Origin (along with a resource website of the same title) and who is an advisor to many curators internationally on the topic of amber.
Elise |
It's always interesting to read these posts by Elise, because she seems to have connections and knowledge from quite a different circle than most mineral collectors and mineralogists, and much of what she describes is "new" to me, and I imagine, to most who read this forum. I'd never heard before of M.C. Pederson, or her book or website about organic gems. Thanks for sharing this info, Elise.
Pete Modreski |
Maggie wrote me last weekend and wished me to add some comments on her behalf to our discussion:
| Maggie Campbell Pedersen wrote: | Copal v. amber. It’s a hornet’s nest! In my understanding that it is the physical and chemical state that determines when the material becomes amber. The youngest amber I have come across is about 12 million years old – but we are waiting to hear from the researchers what age they think the Australian amber is, as it might be younger. The oldest known copal is, as far as I can gather, the new Indian find which is about 52 million years old. Although it has been written up as ‘amber’ it is stated that it is easily soluble in solvents – so it can’t be what we call ‘amber’.
As I understand it, the resin can probably be called copal when it is hard enough to fashion in some way. As long as it can be fairly easily attacked by solvents it is still copal (even Baltic amber can be affected by solvents if left to soak in them). Over millions of years the resin cross links and polymerises, and the volatiles evaporate, making it harder, increasing its melting point, and etc. When it no longer softens when tested with solvents, or melts when tested with a hot point, we say that it is amber. Lab tests such as comparing FTIR spectra can of course also be used to determine the ‘maturity’ of the resin.
But some scientists say that we (gemmologists) are splitting hairs and that either name -- copal or amber -- is correct. Or at least not incorrect. However from a gemmologist’s point of view, we insist on differentiating in order that the general public will not be cheated when they buy the resin, because copal is less durable than amber. It degrades much, much faster.
Re. the origins and the ages of the ambers, the jury is still out. The latest thoughts are that Baltic amber may come from various trees, and be older than thought. The age of Dominican amber is also being discussed. Amber is not an exact science at all.
The Colombian copals that are being autoclaved to make them more durable or to turn them green are being artificially aged. This tends to affect the surface more than the inside of the material, so it still cannot be called amber. And we don’t yet know how durable it is long-term.
I don’t know if this adds anything or gives any info not already known by the FMF group – but I couldn’t resist commenting.
Best wishes
Maggie
P.S. I should probably have written that copal is ‘artificially matured’ rather than ‘artificially aged’. As we know, age has nothing to do with it!
The Colombian copals that are being autoclaved to make them more durable or to turn them green are being artificially aged. This tends to affect the surface more than the inside of the material, so it still cannot be called amber. And we don’t yet know how durable it is long-term. |
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Elise Skalwold |
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