The formation of shell sand depends both on the conditions for growing calcareous organisms, as well as the depositional environment that exists after organisms die. Dating of calcareous shells tells us that the formation of shell sand began at the end of the last ice age, ca. 10 000 years ago, and that shell sand is still being formed today in many coastal areas. Due to the long time it takes to form shell sand, it should be viewed as a non-renewable resource.
Shell sand is most common along the outermost coastal zone where deposition of mineral particles (sand, gravel and clay) is low, and where there is enough wave energy to effectively break down the shells. Generally, the large particles are deposited in shallow water, while the finer particles are led down into deeper water, or protected basins. Shell particles are commonly transported to the lee side of islets and skerries. Shell sand is also common in areas with strong currents, or where there has previously been strong currents and high nutrient levels. The largest deposits of shell sand are found in sites with powerful currents at depths down to 30 meters.
Shell sand is a biotope that serves as spawning and nursery grounds for several species of fish. Large crustaceans use shell sand banks for breeding, molting and to find food.
Shell sand is an important resource several places along the coast in western and northern Norway. In agriculture, shell sand is used for fertilizing. Shell sand is also used to prevent acidification of lakes and waterways, as well as on winter roads to prevent sliding. Due to the continental uplift, since the last ice age, we find shell sand also on land, sometimes several meters deep. In a resource context it is just shell sand with high carbonate percentage and several meters thickness that is of interest to industry.