Long Lost Swedish Blue
While the official name is Bergslaggsten, named for the Bergslagen region of Sweden, due to its difficult pronunciation, the name Swedish Blue was added. Visually, it rivals turquoise or larimar in beauty, but it’s not a typical gemstone. It is not a mineral, nor an organic (like pearl or amber). It is man-made but not a synthetic stone. Swedish Blue is the remnant of a long-abandoned iron smelting technique, making it a a part of history.
Mining, metal smelting and metalworking has been practiced in Sweden since the 11th century. The extraction of iron from rocks mostly since 1180. From the 13th to the 19th centuries, Sweden was a key global iron manufacturer.
During the iron smelting process, different components are extracted from the ore. The melted iron sits at the bottom and slag floats on top. Both are discharged from the blast furnace. This slag can come in a variety of colors and textures. Berglaggsten is a blue colored slag, with swirling patterns and a vitreous texture. Each stone is one-of-a-kind with no two having the exact same colors and patterns.
In the 60’s a goldsmith discovered these blue stones deep in the forests. The slag heaps were covered with vegetation after being untouched for perhaps 300 or more years. He started making jewelry with the stone, but soon realized that high quality stones were limited. Today, a few people have localities in the forests where they collect the stones by hand, usually after storms have caused some erosion of the soil. These spots are a closely guarded secret. The cabochons used for jewelry are all cut by hand, relying on an artistic eye to bring out the beautiful qualities of the stone.
Large Swedish Blue oval pendant in sterling silver, Artisan Jewelry Creations
The material is dominantly glass-like silica. The colors of the stones range from light blue to dark blue and even green to black, depending on other minerals occurring in the stone. In particular, blue-green shades come from the addition of copper.
Round Swedish Blue cabochon in sterling silver pendant. The colors and swirls match perfectly with the blue & silver toned Rainbow Alloy chain. Artisan Jewelry Creations
Besides Sweden, there are other areas where these types of stones have been found. The most famous is the Leland Blue stone from Michigan. It too was created using the same iron smelting process in the mid 1800’s. After going bankrupt, the company dumped the slag into the deep waters of Lake Superior. Pieces of the stone periodically washed up on the beaches. Unfortunately, many tourists later, stones are not easy to find these days. The quality, for use in jewelry, is also inferior to that of Swedish Blue.
Another site, Land Between the Lakes, Tennessee, had furnaces in the 1840s. Most were short-lived. Blue slag can be found on the grounds and trails near the main remnant building but it is forbidden to remove slag, which is considered a historical artifact.
The type of iron smelting that produced blue slag was totally phased out in the late 1800’s due to the development of the Bessemer Process. This revolutionized steel manufacturing - decreasing its cost and increasing the scale / speed of production - allowing for the mass production of steel. Some believe the Industrial Revolution would not have been possible without this invention. Through the late 1800’s old smelting mills either switched to the new method or were run out of business, which shut down the “production” of blue slag. Today, no location in the world produces these stones.