Amber is either "tree" or "drop" amber. Tree amber comes from tree resin secreted, heated by the sun and which hardens as it runs down the trunk. This explains why there are many different shades of tree amber. Drop amber is formed by resin running down icicles. Drop amber can be either rounded, deformed or flattened.
The type of pine tree that secreted the resin grew only in the Baltic area. The resin loss from these types of trees was abnormally high and eventually led to the trees extinction.