It is an unusual event to introduce a new US state to the Eibonvale gallery these days, but here is a first egg from Montana – an Avon thunderegg, collected from the surface of a parcel of private land in Avon. This is not to say that this is the only Location in Montana by any means – I am aware of a few others, most notably several beds in the Bitterroot area, but finding them will be a challenge! For now, this is the first and only Montana thunderegg I have ever seen.
PS. The famous Montana Dryhead Agates, though very nodular, are not thundereggs.