The Stone family

Here you can learn about different rock types. Each member of the Stone Family tells its story of how it was born, where it comes from, and how it ended up here.

If you look carefully among the rounded stones at Mølen and Jomfruland, you’ll find them: Sara Sandstone, Kari Quartzite, Børre Basalt, and all the other members of the Stone Family.

They traveled with the ice sheet and the rivers beneath it, dumped together in a pile on the seabed in front of the glacier. There they remained when the glacier melted after the last Ice Age.
The glacier was so heavy that it pressed the land down, but when it melted, the land rose. This is why the stone pile is no longer on the seabed but on land.
The pile also contained lots of clay and sand, but most of this was washed away by the waves on its way up.

Each member of the Stone Family has its unique story to tell about where it comes from and what it has experienced. Some are used as building materials or for decoration, and they love to share those stories!

Syenite

Synne Syenite, 275 million years old. Syenites are igneous rocks and differ from granites in that they contain much less quartz, or are completely without quartz.

Breccia

“Bølla” Breccia is 580 million years old. Breccias can have very different formation histories, but what they have in common is that these are rocks composed of fragments with sharp edges in a finer-grained matrix.

Gabbro

Gunnulf Gabbro is a plutonic (intrusive) rock, meaning he was once molten deep underground and then solidified into stone. He is composed mostly of dark minerals, with some light minerals as well.

Quartzite

A long, long time ago, Kari Quartzite was a sandy beach, but she has been pressed and heated. That’s why she has changed a bit, but she is mostly made of quartz, just like the sand once was.

Gneiss

Gerda Gneiss is a very old lady who has experienced a lot in her long and eventful life.

Larvikite

Lars Larvikite is very proud to be Norway’s national rock! He is rare, but you can see his beautiful blue color on buildings in many places around the world, because he is really popular.

Pegmatite

Peggy Pegmatite is 280 million years old. Pegmatites are coarse-grained rocks that often occur as veins in, for example, larvikite. They are formed during the final stage when a magma solidifies.

Alunskifer

Conglomerate

Kåre Conglomerate is made up of many different small stones. They have been cemented together with even finer-grained material.

Flint

Fred Flint is not common in our area. He must have traveled all the way from Denmark!

Limestone

Klara Limestone can be seen in the steep cliffs near Porsgrunn and Skien. She is made up of calcareous shells from animals that lived in the sea a long time ago, and contains many fossils.

Sandstone

Sara Sandstone is a cheerful and happy sedimentary rock made up of many small grains of sand.

Hornfels

Harry Hornfels is 300 million years old. The hornfels rocks belong to the group of metamorphic rocks.

Amphibolite

Anders Amphibolite was once a gabbro or basalt, but was transformed after a journey deep underground, where he was heated, squeezed, and pressed

Granite

Geir Granite has been deep down in the earth and is often used for building things.

Basalt

Børre Basalt is a lava rock. He flowed out as molten stone a long time ago, when there were volcanoes in the area. You can find a lot of him on the ocean floor.

Rhomb porphyry

Ragna Rhomb Porphyry is a fine lady who is quite unique. She is a lava that has only been found in three places in the world!

Gea Norvegica Geopark

The Stone family