As society developed through the Middle Ages, the need for materials changed with it, bringing new possibilities for industry and trade. Christianity led to an increased demand for stone material and limestone for mortar. Development and increased agriculture led to a need for iron tools and other materials, laying the foundation for a rich industry in the Telemark and Vestfold areas. The increased extraction of mineral resources, as well as ship building and building materials, also led to a growing timber production in the area. 

 

The geology of the Geopark is very varied, and include a multitude of different minerals and rocks. Iron extraction has been one of the large industries of the area, with several big iron works, such as Fossum Ironwork in Skien, Ulefos Ironwork in Ulefoss and Moholt Ironwork in Siljan. Ulefos Ironworks was started in 1657, and is the only one of the three that is still in production. Today, they mostly produce products like manhole covers. The iron ore in Ulefoss was most suited for cast iron products, and the main production was iron rods that were sold to smiths for further refinement into finished products, such as tools and nails. Other minerals, such as apatite, have also been extracted, as an important phosphorus source in agriculture and fertilizer. 

 

For purifying the iron ore, large amounts of charcoal was needed for the blast furnaces that melted the iron, but also for fire-setting. Therefore, royal privileges were given out to the iron works, requiring farmers to supply charcoal for the production. This played a part in establishing an extensive lumber industry in the area. Lumber as an industry was important for ship building and building materials, where a lot of the wood processing happened at Herre in Bamble. The steep terrain created water falls that were used for powering the saw mills. The coastal location of Stathelle and Langesund provided good locations for harbors and trade. 

 

In 1887, Porsgrund Porcelain Factory was opened, due to the local access to quartz and feldspar which both play a part in porcelain production. The production was profitable already the year after opening, and the products quickly became sought after far outside the region. The Porcelain Factory has established itself as a pillar of Porsgrunns industrial landscape, and is one of few porcelain factories in Europe that still heavily relies on manual techniques for painting and shaping the products.

 

In more recent times, the area has exported large amounts of building blocks of stone. Through magmatic processes in the Oslo Rift 300 million years ago, a unique rock formed, Larvikite. Larvikite is the national rock of Norway, and is only found here in the Larvik area. It has a characteristic blue tint, which is rare in rocks, making it a popular choice for facades and other decorations. Therefore it is a sought after building material and can be seen on the UN-building in New York, as well as many other countries.

 

Society is still discovering new natural resources in the area of the Geopark, like on the Fen Field where a large occurrence of rare earth metals have been discovered. These metals are important for the production of microelectronics, such as data chips, and thus plays an essential part in the production and development of modern technology. Today, the majority of these metals are extracted in China, making the current situation vulnerable from a geopolitical point of view. Therefore, this discovery is of international importance and can turn into a new industrial adventure, bringing the rich industrial history of this area further into the future.