Resin secreted by coniferous trees at least 40 million years ago was carried southwards by rivers from the territories of Scandinavia and the present-day Baltic Sea and laid down in Paleogene marine sediments known as blue earth. These blue earth deposits accumulated in a delta at the mouth of an ancient river known by the mythical name Eridanus, which emptied into the Eocene Sea. On the Sambian Peninsula in Russia, Baltic amber has been extracted directly from this Paleogene deposit, from a maximum depth of 50 meters (ca 164 ft), almost continually since the 17th century. In the Polish section of the delta, near Gdańsk, the same deposit lies at a depth of around 120 meters (ca 393 ft), which at present precludes its exploitation.
Succinite just as suitable for working as that found in the Baltic region was also deposited in Paleogene sediments along the southern edge of the Eocene Sea. At least two Paleogene deltas are known to have existed: the Parczew delta in Poland and the Klesov delta in Ukraine. The size of the amber deposit in the Parczew delta, has been estimated at over 7000 tons. This deposit lies at a relatively shallow depth, making it accessible for extraction, although it has not been exploited to-date. Succinite also occurs in central Germany, though here it is found in younger deposits (Upper Eocene–Lower Miocene) than amber in the Baltic region and in Ukraine. In 1974 amber was discovered in the Goitsche Paleogene coal mine. Nearly 50 tons a year used to be extracted from this, now disused, mine.
During the last one million years — the Quaternary period — amber from Paleogene deposits was transported over considerable distances by glacial, fluvial and fluvio-glacial action to new locations in Poland, Belorussia, Lithuania, Latvia, Germany and even as far as the east coast of the British Isles, Jutland and the southern coast of Scandinavia. In the Holocene, and indeed at present, nodules of amber subjected to the effects of storms in the Baltic were deposited on beaches and naturally rounded by wave action. Around 30 tons of amber are washed up annually along the coast of Scania. In Poland approximately 4 tons are collected from the beaches every year. Identifying the presence of amber within Quaternary sediments by geological prospecting is only practicable in certain areas of Poland, e.g. the youngest Holocene beaches of the Baltic coast. Nevertheless, whilst working on a distribution map of amber found in Poland it was established that occurrences of this fossil resin have been recorded on at least 750 occasions.
In geological deposits amber occurs in specific natural drip forms, such as stalactites or drops, or else as forms which were created within crevices inside strongly resiniferous trees. Amber nuclei which formed within fissures, either in the bark or beneath it, or even between a tree’s annual growth rings, constitute a fossil of sorts (sometimes of remarkably large size) evidencing the existence of long-vanished trees. Some nodules formed from resin accumulations inside fissures weigh 2–5 kg. The largest one recorded so far weighs 9.75 kg and is housed at the Natural HistoryMuseum of Humboldt University, Berlin. Amber which has been transported over long distances or polished by wave action occurs in the form of rounded pebbles or small grains.