FMF - Friends of Minerals Forum, discussion and message board

[alfredo]

Well, if it's from Tertiary coal, then it must be amber, and not resin/copal.

[Elise]

[Pete Modreski]

[Elise]

Hi,

Thank you Pete -- I was interested in Alfredo's concern regarding definitions and dmg's insights - It was just a timely subject in terms of my own research into the problems surrounding environmental controls for displaying amber specimens for the public. I've been corresponding with several curators about how to safely handle amber - closed environments, chemical humidity controls (for organics), horror stories about collections disintegrating. As with mineral collections, insights from private collectors can only widen the knowledge base. And as Alfredo pointed out, without a good definition, or one that people agree on, it makes life harder. I don't know if FMF membership includes many other people collecting amber (jump in here anytime Mark), or whether it even belongs in your forum....I thought for sure someone would pick up on my quotation above of Chhibber in which he called amber a mineral.....and run with it.

I took the question of "copal" as a homework assignment that had me digging through everything from my ratty copy of the 1993 Smithsonian cover story on amber to many books and journal articles relating to the subject. I came away with the feeling that I'd walked into a historical hotbed of semantics while having a small walk-about in etymology regarding terminology for resins. I didn't know that at one time the attempt was made to limit "amber" only to Baltic succinite..."true amber." (Weitschat and Wichard, Atlas of Plants and Animals in Baltic Amber).

Andrew Ross, curator of fossil arthropods at the Natural History Museum, London, wrote in "Amber: the Natural Time Capsule" (which has a nice dichotomous key for inclusions) that most believe the polymerization of resin to amber is dependent on time, but pointed out that "types of sediment in which the resin is deposited is much more important than time for amber formation. ...what is not so clear is the effect of water and sediment chemistry on the resin." (this was in reference to resin in sandstone vs that in clay beds). He describes resin fresh out of the tree as merely hardened resin which then starts to polymerize when it is buried in sediments; "copal" is between "hardened resin" and completely polymerized inert "amber." (but is that process really complete?)

Dahlström and Brost in "The Amber Book" have a detailed chapter titled "A stone or not a stone? a matter of semantics" which goes into the history of all the terms related to amber/resin/copal. Later in the book there is discussion of copal - "hardened resin" which "may be millions, thousands or merely hundreds of years old....One of the oldest kinds of copal comes from Mizunami in Japan" (330,000 years). I don't find other reference to copal millions of years old in that text; perhaps that is an error. They also point out that in Germany resin products under 20 million years old can't be sold as amber, though in the authors' country (Sweden), there isn't a formal regulation regarding age (1996).

In The American Museum of Natural History book "Amber Window to the Past" by David Grimaldi, a section titled "Copal" starts a paragraph with "confusion surrounds the use of the term copal..." It also points out that the oldest copal deposit is that of Mizunami, but gives its age as 33,000 years. The term "resinite" is given as one which geologists use to for "any hardened resin, whether amber or copal"....sounding closely to "retinites" defined in Weitschat as all other fossilized resins other than Baltic succinite. A reference is made to East African copal which "may be 2 million years old, but this is very unlikely." (no citation, but perhaps a lead to the reference Maggie made which I haven't asked her about yet). Just as an aside to the age of Burmese amber, D.A. Grimaldi is one of the people who has published research which updates Chhibber's report of the 30's amber fields - both are widely quoted in other publications, not necessarily together and maybe confusing some.

Dr. Rice in Amber The Golden Gem of the Ages, talks about "true copal" as semi-fossilized resin ranging from "over 1,000 years to as little as 100 years old" (fresh gum from a tree is "raw copal" ). She quotes George Poiner's (Life in Amber) definition of copal "a recently deposited resin that can be distinguished from amber....by its physical characteristics...including hardness, specific gravity, melting point and solubility." and she further states from him "that deposits younger than Tertiary Period (or less than 2 million years old) fall into the copal category."

Along with other passages in books and papers, it seems there isn't much agreement about age. But somewhere back in all that reading, along with several models for visualizing the continuum and agreement that the polymerization process has a lot of variables, I ran across such statements as: "copal" is younger than 1 million years (or "amber" is older than...); amber can be attacked with sulfuric ether and other solvents with difficulty (as opposed to copal which is readily attacked) and that amber isn't completely inert after all. I only referenced readily available books that people may run across. There is much in the scientific literature, for example a nice discussion covering the chemistry and structure of amber vs copal included as an appendix to a paper on green amber by Ahmadjan Abduriyim et al (Gems & Gemology, F09); the whole series of papers by Ken B. Anderson titled “The nature and fate of natural resins in the geosphere” and any of the papers by David Grimaldi, to mention just a few - but still some disagreement.

All that is to say, I can't find a good definition of "copal" and maybe even "amber" is a bit vague.

Cheers!
Elise

[Pete Modreski]

Thanks again for all the comments, Elise. I'm going to be sure to read that article & summary about "resinite" in the F09 Gems & Gemology that you referred to.

This has ever (What is amber?) been a very confusing subject, to I think just about everyone who has ever tried to read about it. I once heard a talk on amber by a USGS staff member (a part-time volunteer actually, who'd been studied this as a side interest) who been doing some chemical studies on amber; I must say, his talk left me, and probably most of the audience, more confused than when he'd begun.

I believe that some "authoritiative sources" say that "true amber" only came from a certain type of tree, that grew in the Baltic region, and that other resins, from elsewhere in the world from other (related, but not the same) species or genera, just are not the same and are not real amber. (I know I'm oversimplifying this, to say it this way.) Perhaps, there are some semantics involved in the definition of "amber".

I'd say that most people in this Forum "pretty much" would accept amber as a valid topic for discussion--even if, of course, it isn't a proper "mineral" in the strict sense.

Pete

[alfredo]

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.

[Elise]