During the First World War, 514 tonnes (506 long tons; 567 short tons) of apatite was mined and transported by rail from Blakstad to Arendal.
Selama Perang Dunia I, 514 ton (506 ton panjang; 567 ton pendek) apatit ditambang dan diangkut dengan kereta dari Blakstad menuju Arendal.