Very Large 30 Pound Amber or Copal?

[hertzyinmn]

Hi, I was hoping for some expert advice on this item, I was in process of a purchase of this piece from a lifetime collector .Story is that he purchase this from a gentleman back in the 80s who needed money.He was told that the man found it up north somewhere, Being in Minnesota I thought maybe this could be a piece of Ceder Lake Amber from Manitoba Canada. I have done an Acetone test, and then An Ethel Alcohol test and it seems to eveporate and does not seem to get tacky so I believe it to be Authentic but am not sure, It is about 2Feet by 1 Foot and wieghs in around 30 Pounds on a bathroom scale. He wants a Pretty hefty price But I havent seen such a large Amber item such as this., i did take some blacklight pics if anyones interested let me know and I will post them . Thanks

[2ndoldman]

Boy that is a good question. I have never seen amber in an almost crystalline structure before.

[painshill]

That’s a very interesting chunk of material!

Bruce is partly correct in saying that amber doesn’t usually have a crystalline structure. In fact it never has a crystalline structure. By definition, it’s “amorphous” (non-crystalline). However, I don’t see any crystalline structure here. What I see is a layered/laminated structure of something with a weakly conchoidal fracture. That would be consistent with some types of amber… notably deposits from coalfields, which are sometimes referred to as “resinite amber”.

The most extensive deposits of that kind of material “north” of Minnesota come from the six coal seams that make up the Late Cretaceous Taber Coal Zone throughout Western Canada, and especially the outcrop at Grassy Lake, Alberta where the deposits have been further exposed by coal-mining. There are patchy deposits of dark yellow amber within the sub-bituminous coal and in the organic-rich shales overlying it, but a piece as large as yours would be an extraordinary find. The exposed host layers are only about two feet thick and about a foot thick respectively and much of what has been collected is from the broken-up mine tailings that litter the area.

It’s unlikely to be Cedar Lake material. Those deposits (on the western shores of the lake) have come from the same sources but they’re placer deposits representing a derived secondary occurrence that has tumbled far downstream in ancient times. As such, the amber pieces are significantly smaller and generally darker, often with a very dark weathering rind.

Usually this material is very rich in organic inclusions (mostly insect remains plus some plant debris), so it would be worth having a good look with a decent loupe. In a piece as large as that, there ought to be something. There may well be other coal deposits that could yield such material without the high level of inclusions.

It’s good that the material has passed the acetone test but – as you probably know – it’s not diagnostic for amber. It just distinguishes amber from some other materials that could be mistaken for it (sub-fossil resins such as copal and some plastics). It won’t rule out all plastics, other minerals, or things like slag glass.

Amber is not much denser than water and significantly less dense than other lookalike minerals or slag glass. I know you’re only giving approximate dimensions and weight but they look to be consistent with amber. Resinite from coal deposits tends to be at the lower end of the density range for amber and so a piece weighing around 30 pounds that’s around two feet by a foot would need to be a little under 3 inches in thickness (or any combination of dimensions that gets you to about 790 cubic inches) to be consistent with that kind of density.

I would say it looks good for resinite amber from a coal deposit, although there’s only so much that can be said from the pictures and information provided. If the seller is happy about it, the red-hot pin test in an inconspicuous area would confirm it to be amber (the pin should penetrate with difficulty, leave a blackened residue and produce a pleasant but weak aromatic odour).

If you have access to a UV “black light” (of the kind used by Dee-Jays for example), checking for fluorescence might give you a little more information. Most ambers will fluoresce with typical bright colours of yellow, orange, blue or green. Ambers with naturally darker colours (in daylight) tend to fluoresce less strongly or may only have fluorescent flecks within the specimen. Copal does not usually fluoresce at all and if it does, it will be very weak. The nature of the fluorescence is frequently locality-dependent and Canadian amber is generally reported as having green fluorescence that may be even be strong enough to be visible as a mild green hue in ordinary bright sunlight.

[hertzyinmn]

Hi, Thank you very much for all the information that was very informative . I did do a red hot needle and It did slowly protrude into it. I had to push a bit and it was not a quick melt but it went in, Also here are a couple of black light pics it seems to have a greenish blueish hue . Well I Think I may take a small sample and send to The GIA before I spend to much On this . Anyway thanks again Mark

[clovisoid]

What did the pin test smell like? I believe the key is a nice odor vs smelling like melted plastic/burnt hair.

[hertzyinmn]

Yeah I really didnt think abount sniffing it I just wanted to make sure it penatrate like it should for a fossilized resin . I may try to take a small piece and it should burn like an incense i read

[painshill]

As I said, you should get a “pleasant but weak aromatic odour”. Amber does burn (or at least smoulder) rather than melt, usually producing a whitish smoke and leaving a blackened residue. Ambers from the Americas are most commonly derived from the resins produced by pines of the Araucariaceae family and so generate a typically piney odour. Araucaria of the genus Agathis were long-speculated to be the source trees for Canadian material from the Taber Cola Zone, but recent research suggests that’s probably incorrect and the source trees were probably extinct cypress conifers of the genus Paratoxodium. The odour is less less pine-like in that it’s spicy and sweet, sometimes with notes that are juniper-like. The Canadian material is also Late Cretaceous and so will likely be more polymerised and oxidised, leading to a weaker odour than you would get from more recent ambers from the Eocene.