Hell Creek Formation amber

Amber from the Hell Creek Formation of Montana (upper Cretaceous)

Hell Creek Formation amber in a lignitic shale matrix, eastern Montana, USA © 1997-2010 Phillip Bigelow A typical example of amber from the Hell Creek Fm. of Montana. Reddish-orange varieties (photo left) to deep red varieties (photo right) are the most common colors found in the Formation. Yellow color varieties are present, but they all have a powdery appearance, and may represent amber that has been oxidized. Oxidation causes amber to become opaque, yellow, and crumbly (photo left). So far, I have not seen any uncolored transluscent varieties. The Hell Creek Formation amber is mainly found in shaley zones with interlaminated lignite. Compared to Tertiary-age amber, the Cretaceous-age Hell Creek Fm. amber is less abundant and is smaller. The material that I have seen is EXTREMELY friable (friable = easily crumbles). This amber is so fragile that it will sometimes crumble into dust if you try to pick it up with tweezers or even with your fingers! The specimen was not coated with any preservatives, but I have put preservatives on other Hell Creek amber, particularly if the pieces are going to be handled. Preservatives darken the amber significantly, and I have found that they impart an undesirable appearance. Both shale zones and lignitic zones (the strata where Hell Creek Fm. amber is most likely to be found) are uncommon in the Formation. Most fine-grained Hell Creek rock is a massive mudstone, and the likelyhood of finding amber in this Hell Creek rock type is quite small.

There are some claims that genera in the Araucariaceae are the source flora for much of the Hell Creek Formation amber (living examples of this ancient plant group are the Monkey Puzzle tree and the Norfolk Island Pine), although no detailed scientific study of the geochemistry of the Formation's fossil sap has been done. It is quite possible that other taxa are also sources. Many scientific discoveries from the Hell Creek Formation of the northern Great Plains still await paleontologists and geologists.

Not all Hell Creek Formation amber is as diminutive as are the specimens I have illustrated here. Check out an article in the November, 1993 issue of Lapidary Journal (page 41).