The composition, color, and other physical properties of amber all vary according to age, conditions of burial, and type of tree that produced the resin. Amber has been found in sediments from the Carboniferous to Quaternary age, but the greatest concentration is in Cretaceous and Tertiary sediments. It is difficult to determine if the amber in sediments is primary or secondary.
Primary deposits are insitu.
Secondary deposits are where amber is found after transportation by rivers, transgressing seas, glaciers or fluvioglacial waters. Up until 1860 amber procuring methods were off the beaches and with shallow diving. It was obvious that sea amber came from strata beneath the sea and a larger supply could be obtained by dredging or mining. Most Baltic amber is being produced in the Samland promontory, an area today controlled by Russia, where the strata containing amber is approximately 25-40 meters beneath the soil. Controversy exists regarding the geologic age of some resins, and whether or not all fossil resin may be considered amber.