August 2018 Issue Table of Contents
Lithium – 200 Years
Symposium and Field Trip June 14–16, 2018
Lithium was discovered in 1818 in petalite from pegmatites on Utö (Sweden), an island in the Stockholm archipelago, by Johan August Arfwedson (1792–1841), a student working in the laboratory of Jacob Berzelius (1779–1848), the famous Swedish chemist. To commemorate the 200th anniversary, the Swedish Mineralogical Society (SMS), with the support of the Swedish Museum of Natural History, organized a symposium held at the museum (Fig. 1) followed by a two-day field trip to Utö Island, where it is still possible to collect petalite and other lithium minerals and to study the geological context of the lithium–cesium–tantalum (LCT) pegmatites in which the lithium minerals occur.
The symposium opened on 14 June 2018 before an audience of more than 40 with a welcome and introduction by Erik Jonsson (Geological Survey of Sweden and Uppsala University), who also touched upon the economics of lithium as a potentially critical commodity in Europe. The keynote talk was delivered by Edward Grew (University of Maine, USA) on lithium mineral evolution and ecology, i.e. the increasing diversity of lithium minerals as reported in the geologic record, the history of discovery of these minerals, and estimating Earth’s endowment of these minerals. Andreas J. Korn (Uppsala University, Sweden) discussed lithium in the cosmos. This talk was followed by reviews of lithium mineralization in Norway, by Roy Kristiansen (amateur mineralogist from Norway, delivered by Alf Olav Larsen), and in Swedish pegmatites, by Erik Jonsson. Joakim Mansfeld (University of Stockholm, Sweden) reported on the metamorphic evolution of the rocks that host the LCT pegmatites at Utö, and Jörgen Langhof (Swedish Museum of Natural History) summarized studies of these pegmatites. Magnus Leijd reported on Sweden’s most recently discovered LCT pegmatites at Bergby, and Thomas Zack (University of Gothenburg, Sweden) concluded the symposium with a re-evaluation of Swedish pegmatite ages using in situ Rb/Sr dating.
Following the symposium, 18 participants attended a field trip to Utö Island to view the famous Swedish iron-ore mines and the LCT pegmatites at the type locality for petalite and spodumene. Participants gathered at Årsta havsbad (a port on the coast south of Stockholm) for the ferry to Utö and enjoyed a picnic lunch in splendid weather at the first stop in Rävstavik. Here, participants observed glacially polished coastal outcrops of metagreywacke intercalated with metaconglomerate at the base of the sedimentary–volcanic sequence that hosts the LCT pegmatites. After a brief examination of metasedimentary and metavolcanic rocks higher in the section, participants admired the Nyköpingsgruvan and Långgruvan mines. From at least as early as the 12th century, and only ending in 1879, iron ore was extracted from these mines, which are now partially filled with water. The LCT pegmatites located within these mines are where several lithium-bearing minerals were discovered: spodumene and petalite (in 1800) and holmquistite (in 1910). The largest LCT pegmatite is, for the most part, submerged, but a smaller dyke to the south afforded views of the contact in situ between host rock and pegmatite (Fig. 2). This part of the pegmatite shows patches of amazonite and there are spodumene cleavages up to several centimeters across. The day’s field activities concluded with a stop at the most differentiated part of the bigger Nyköpingsgruvan pegmatite where pollucite, a cesium-rich zeolite, has been reported. The final “stop” was the small mining museum in the “Spruthuset” building, which was specially opened for our benefit. At 18:00, participants were treated to a lecture by Jan Trofast on a re-evaluation of the history of the lithium discovery based on his latest research on J. Berzelius. The second day was largely devoted to collecting on the main mine dump, where participants succeeded in finding several of Utö’s specialties – fresh petalite, fibrous holmquistite (Fig. 3), chiavennite, and elbaitic tourmaline.
Edward S. Grew, Erik Jonsson, and Jörgen Langhof