Baltic amber

This region's forests produced an estimated hundred thousand tonnes of resin, and people are still pulling four hundred tonnes a year out of the ground.

Baltic amber, properly succinite, is amber from the Baltic region, which holds the largest known deposits anywhere. It formed during the Eocene, though exactly when within that epoch is still argued over. Today more than 90 per cent of the world's amber comes from Kaliningrad Oblast in Russia, where it is a serious source of regional income: the Kaliningrad Amber Combine extracted 250 tonnes in 2014 and 400 tonnes in 2015. It is also found in Poland and across the Baltic states.

The name succinite is not decoration. Baltic amber contains between 3 and 8 per cent succinic acid, which is a chemical signature, and that signature is how look-alikes get sorted out. Bitterfeld amber, from the brown coal mines near Bitterfeld in Germany, was long assumed to be Baltic amber that had simply been moved and redeposited. It is now known to be chemically distinct, although like Ukrainian Rovno amber it seems to have been laid down around the same time.

In place, the amber sits in the sediments of the Prussian Formation, which older literature calls simply the Amber Formation.

Beyond jewellery, it matters for what is trapped inside. Baltic amber is one of the richest fossil archives of insect life in existence, and new species are still being described from it: in 2011, Stylianos Chatzimanolis of the University of Tennessee at Chattanooga and Michael S. Engel of the University of Kansas published a new species of the rove beetle genus Diochus from Baltic amber in the journal ZooKeys. Every piece with an inclusion is a snapshot of a forest floor tens of millions of years old.

Beachcombing after storms is the traditional way to find it on the southern Baltic shore. Amber is light enough to be moved by water, which is why it strands. Local rules on collecting vary by country, so check.