Magnetite
Magnetite is an iron oxide, and next to hematite it is the most important iron ore. The mineral is black, fairly hard (roughly like a knife blade) and strongly magnetic. While hematite leaves a reddish-brown streak, magnetite’s streak is black. Magnetite is the type of iron ore that was extracted in the Arendal area, and the exhibited sample is from the Bråstad mine.
There was operation in various mines in the Arendal area from approx. 1574 to 1975. The estimated total production was approx. 1.3 million tonnes of iron from 3.3 million tonnes of ore. The iron mines around Arendal laid the foundation for Næs iron works in Holt, Egeland iron works in Gjerstad and Froland works, but also supplied ore to, among others, Moss and Bærum.