Nordic Gems and Jewelry
At the JOGS show, Arctic Jewelry (Axvalla, Sweden) featured a variety of Nordic gemmy materials set mainly in silver using ancient, traditional, and contemporary Scandinavian designs. The pieces spoke to the mineral diversity, history, and artistry of the region.
The Vikings made navigation stones from locally sourced transparent crystals of minerals such as cordierite, a biaxial magnesium iron aluminum silicate, to help cross the seas under cloudy weather. These Viking “sunstones” are backed up by science, as cordierite and other materials such as calcite and tourmaline can be used to identify the position of the sun through even thick clouds. These stones visibly split sunlight into two images that when rotated to make equally bright, show rings of polarized light around the sun’s position. Cordierite was found to be the most accurate navigation stone in simulated journeys from Bergen, Norway, to the Viking settlement of Hyarf in Greenland (D. Száz and G. Horváth, “Success of sky-polarimetric Viking navigation: revealing the chance Viking sailors could reach Greenland from Norway,” Royal Society Open Science, Vol. 5, 2018, No. 172187). An example of a silver pendant engraved with a vegvísir (a Nordic compass “wayfinder” symbol) and a cordierite center stone was shown to us by Atle Berger (figure 1).
Thulite, a manganese-containing pink variety of zoisite with some white calcite mottling, is the national gemstone of Norway, the country in which it was discovered by Anders Gustaf Ekeberg in 1820. The name comes from “Thule,” the ancient name for the mythical island (believed to be modern-day Norway) that was considered the northernmost part of the world. At the Arctic Jewelry booth, contemporary Scandinavian designs in silver incorporating this stone were featured in jewelry ranging from rings to bracelets and necklaces (figure 2).
A bright and attractive blue material found at the booth is the slag byproduct of iron smelting in the Bergslagen region of central Sweden during the Middle Ages. This material was reported on previously in G&G (Winter 2006 GNI, p. 279) and characterized in the GIA lab. At that time, EDXRF was the method used for chemical analysis, but today with LA-ICP-MS we were able to more exactly determine the composition of this material from some rough pieces given to us by Mr. Berger (figure 3). We identified it as a silica-rich glass with a composition of 56.35 wt.% SiO2, 24.70 wt.% CaO, 7.68 wt.% MgO, 5.05 wt.% Al2O3, 2.23 wt.% FeO, 2.21 wt.% K2O, 0.85 wt.% MnO, 0.27 wt.% Na2O, and 0.65 wt.% other elements (average of 10 ICP spot analyses). This gave a calculated chemical formula of (Na0.019, Mg0.418, Al0.217, K0.103, Mn0.026, Fe2+0.068, others0.012)0.864 Si2.058 Ca0.967O6, which is generally consistent with what was reported in 2006. The oxide components are fairly normal for iron foundry slag, but the silica-rich nature is what gives this material its fine glassy aspect compared to those slags that are more CaO-rich. The slightly greenish blue color comes from Fe2+ (FeO).
