Siggjo is a cone-shaped, volcano-like mountaintop in the part of Hordaland where one finds the best preserved volcanic rocks. The rock types originate from one or several volcanoes that spewed out glowing lava and ash. But, the shape of the mountain, as it appears today, formed later and by completely different forces.
In 1868 the first stone workers came to Rubbestadneset to take out the granite for the Skoltegrunns Pier, predecessor of the Skoltegrunns wharf in Bergen. Later granite was also taken out from the area, around Innværs Fjord and UransvågenN. The activity probably peaked around 1900, with over 40 men at work. 15 years later, it was finished.
If we study the group of islands south of Selbjørns Fjord from the air or on a sea map, we will notice that many of the islands are elongated and lie systematically in rows. The islands are divided by long sounds, for example Trollosen, Nuleia and Hjelmosen, which are oriented in a south-southeast to north-northwesterly direction.
At Flintaneset by Finnåsvika, in the centre of the municipality, we find the most beautiful and best preserved igneous rocks in western Norway. We must go to Hawaii or Island to find as fine structures as at Bømlo.