Danish amber, the Jutland coast

Baltic amber is fossil resin from conifer forests that grew across northern Europe in the Eocene, roughly forty four million years ago. It is not a mineral. It is tree resin that lost its volatiles and polymerised, which is why it is warm to the touch, floats in strong salt water, and burns with a smell of pine.

The Baltic material is scientifically important for its succinic acid content, up to about eight per cent, which is why the mineralogical name for it is succinite. It is also the reason so much of it holds inclusions: resin flowing down a trunk traps whatever is on the bark, so Baltic amber has preserved an entire Eocene insect fauna in three dimensions, with detail no compressed fossil can match.

Denmark gets its amber second hand and by sea. The primary beds are offshore and to the east, and North Sea storms tear amber out of the seabed and throw it onto the Jutland beaches. The west coast is the ground: the long sand between Blåvand and Skagen, and the beaches of Fanø and Rømø.

The technique is simple and the timing is everything. Go after a hard westerly blow, in the cold half of the year, and walk the strandline where the seaweed and light debris have piled up, because amber has almost the same density as that material and sorts with it. Look for a dull, waxy orange-brown lump rather than a jewel; polished amber looks nothing like beach amber. It is light in the hand, which is the giveaway against pebbles.

Danish beaches are open to the public and beachcombing for amber on the strandline is normal and accepted. Take a torch: many collectors work at first light or after dark with an ultraviolet lamp, because amber fluoresces and phosphorite, its main lookalike, does not.

One Danish law is worth knowing before you go. A fossil or a meteorite found in Denmark with unique scientific or exhibition value is danekræ: it belongs to the state, and the finder must deliver it straight away to the Natural History Museum of Denmark or a recognised local natural history museum. The finder is paid for it, and paid more for a specimen that has been looked after.