Alnön is an island in the Gulf of Bothnia just outside Sundsvall in Medelpad, Sweden. It has an area of 65 km² and a population of 7,951 (2005-12-31), which in summertime doubles. Most inhabitants work in Sundsvall and other towns on the mainland.

The island is 15 km long and 6 km wide on the widest spot. It is connected to the mainland by a 1,042 meter bridge, which was the longest bridge in Sweden when it was opened in 1964.

Alnön was populated already during the Viking Age, and there are several tumuli on the island from that period. The old stone church near the modern bridge was built in the 12th century.

The island saw a population boom in the second half of the 19th century, due to the development of steam driven sawmills. In 1850 the island had 950 inhabitants, mainly farmers and fishermen, but by 1900 the population had grown to almost 7,000, following the establishment of 18 sawmills between 1860 and 1897.

Geology

Alnön was formed some 570 million years ago through a massive volcanic eruption. The ground is lime rich, and it is one of a very few areas in the world with a alkaline volcanic area. It's chemistry is very different from the ordinary granitic rock in the region, resulting in a number of unusual minerals, such as borengite, baryte and aegirine.

The most famous of the Alnön minerals is the rock 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. Perovskite, apatite, nepheline and garnet may also be present. Diamonds have also been found on Alnön, but only in very small amounts.

Links

Rock samples from Alnön