The Dala (Aelvdalen) Porphyries from Sweden

The commercial stone industry in Aelvdalen, northwest of Stockholm, started in the second half of the 18th century as a social need. The region had been plagued by severe famine and there was an urgent need for additional wealth-generating industry. At that time it was already known that the porphyry in the area was similar to the "porfido rosso antico" from Egypt which had played an important role in the Roman culture. Many ups and downs followed. During one period in the 19th century, the Swedish Royal family owned the industry. At the same time, several "porphyry" objects were presented to different courts around Europe (e.g. a 4 metre tall vase to the Russian czar, although of a more granitic variety). Otherwise most products have been smaller objects like urns, vases, candelabras, etc. The very hard Stone (with variable red or black colours) can be highly polished. Many of the porphyry varieties were sourced from glacial boulders. These had been "mechanically tested" by nature and were free from joints which otherwise was a problem in the associated quarries. Comagmatic granites also occur. The porphyries and granites have an age around 1700 Ma, and the former are amazingly well preserved with magnificent volcanic textures. The porphyries and granites occupy a vast area and are in part covered with red, continental sandstones, which are quarried to-day. In the middle of the 20th century, the ignimbritic character of the porphyry was discovered. Previously, the flattened "fiamme" (collapsed pumice) had been interpreted as some kind of flow structure in lava. The porphyry manufacturing plants in Aelvdalen are a part of the Swedish industrial history. Over a significant historical period the porphyry-works produced good handicrafts that catered for the poor as well as providing items of extravagant luxury. Today a porphyry museum exists in Aelvdalen. A few handicraft workers are active, and the abandoned old porphyry plants are open to visitors.