As result of decreased foreign trade during World War II apatite was mined in Alnön from 1943 to 1945.

[2] While the separation process had improved in 1945 the end of the war the same year meant also apatite mining became unprofitable.

The northeastern part of the island is rich in carbonate minerals, and it is one of few areas in the world with a carbonatite volcanic complex.

[3] Its chemistry is very different from the ordinary granitic rock that form the rest of the island, resulting in a number of unusual minerals, such as baryte and aegirine.

[4] The most famous of the rocks of Alnön is the alnoite, named from the Island, which is a lamprophyre chiefly composed of biotite or phlogopite and melilite as essential minerals, commonly with olivine, calcite and clinopyroxene.