By Lord Alan MacFarlane, Royal Scientist
This project is my interpretation of a possible Viking era sunstone necklace using period-correct glass beads and bronze wire. The item would likely have been worn by a seafaring woman of high importance 12.
The Viking Sunstone is a type of natural mineral known as calcite or Iceland Spar. Calcite (calcium carbonate) has a polarizing effect on sunlight due to the double refraction property of the mineral. The sunstone has been postulated as being used in the Viking Age to locate the sun in a completely overcast sky, or when it was on the edge of the arctic horizon 1. It is also known as an Alderley stone 2.
The sunstone (sólarsteinn) is mentioned in two historical Icelandic texts: Rauðúlfs þáttr (14th-15th C) 3 and Hrafns saga Sveinbjarnarsonar (13th C) 4 . Church and monastic inventories show that something called “sunstone” did exist in medieval Iceland. The sunstone can also be used as a sort of sundial and would have been useful to keep track of canonical hours 5 as well as at high latitudes and in mountainous areas.
Rauðúlfs þáttr describes the stones usage in such detail that the idea of using them to find the sun’s position in overcast conditions was commonplace:
“The weather was thick and snowy as Sigurður had predicted. Then the king summoned Sigurður and Dagur (Rauðúlfur’s sons) to him. The king made people look out and they could nowhere see a clear sky. Then he asked Sigurður to tell where the sun was at that time. He gave a clear assertion. Then the king made them fetch the solar stone and held it up and saw where light radiated from the stone and thus directly verified Sigurður’s prediction. 8”
Thorkild Ramskou, a Danish archaeologist postulated that the sunstone could be calcite, a mineral that polarizes sunlight and by which the azimuth of the sun could be determined in overcast skies in 1967 1. Research performed in 2011 verified this, and proved that Iceland Spar (optical calcite from Iceland) could indeed be used to determine the direction of the sun to within a few degrees in overcast conditions 6.
An Elizabethan era ship that sank near Alderley in 1592 held a piece of Iceland Spar 2. It has been suggested that the sunstone was used along with the magnetic compass for navigation. The sunstone would have been useful in areas of strong magnetic deviation and would have been unaffected by such areas 9. Vikings could have utilized them in Northern latitudes where it never became completely dark in summer 7.
The stone takes some skill to use. It is operated by placing a mark on top of the crystal. When viewed from below two marks appear because of the double refraction. The stone is rotated until the two marks have the same luminosity. The angle of the top face now gives the direction of the sun. Historically, tar or pitch may have been used to make this mark 7.
Modern analytical methods were used on the modern bronze wire utilized, plus on an actual bronze artifact from period times for comparison. X-ray Fluorescence (XRF) is a non-destructive analytical technique. It uses high energy X-rays to excite the elements in a sample. The instrument then records the characteristic emitted signal of those elements. This is the method that major institutions like the Smithsonian and the British Museum use to test archaeological items. The instrument used here was an Olympus Vanta Element VCR handheld unit.
Bronze was chosen as an affordable material that was used at the time.The modern wire is clearly a “clean” phosphor bronze. There are few trace elements present. Notably, zinc, lead and iron are below detection limits. I also performed an XRF analysis of an actual Rus’ Viking bronze ornament from approximately 1000 CE owned by Master Patris de Terra Lepori and compared the results. The period metal looks very different in composition. It contains some zinc, iron, silver, lead, and other trace elements besides the usual copper and tin.
It is likely that most genuine period Viking bronze would have been similarly varied in composition due to the material coming from varied sources. I would speculate as a metallurgical chemist that wire of this sort of antique composition would behave differently and could be more difficult to cast and work with. However, some of the trace elements present may also resist corrosion better than modern phosphor bronze. More research is needed here.
This example is strung with glass beads. Two of the beads (striped blue/white and red/black) were custom made for this piece by glassworker Rebecca Jinette of Bertie County, NC. I chose beads that had a similar appearance to period beads available to the Vikings as seen in my research 11.
Sunstone References
- Ramskou, Thorkild (1967). “Solstenen”. Skalk (in Danish). 2: 16–17.
- Satter, Raphael (March 8, 2013). “Researchers: We may have found a fabled sunstone”. Yahoo! News. Associated Press.
- Turville-Petre, Joan E. (Trans.) (1947). “The story of Rauð and his sons. Payne Memorial Series II. Viking Society for Northern Research. ISBN 0-404-60014-X.
- Helgadóttir, Guðrún P (ed.). 1987. Hrafns Saga Sveinbjarnarsonar. Oxford: Clarendon Press. ISBN 0-19-811162-2. 267 pp.
- Einarsson, Árni. 2010. Sólarsteinninn: tæki eða tákn. (Summary in English: Sunstone: fact or fiction). Gripla 21 (1) 281–97 Árni Magnússon Institute. ISSN 1018-5011.
- Ropars, G. et al., 2011. A depolarizer as a possible precise sunstone for Viking navigation by polarized skylight. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science.
- Bernáth, Balázs; Farkas, Alexandra; Száz, Dénes; Blahó, Miklós; Egri, Ádám; Barta, András; Åkesson, Susanne; Horváth, Gábor (26 March 2014). “How could the Viking Sun compass be used with sunstones before and after sunset? Twilight board as a new interpretation of the Uunartoq artefact fragment”. Proceedings of the Royal Society A.
- Vilhjalmsson, Thorsteinn. 1997. “Time and Travel in Old Norse Society Archived 2016-03-03 at the Wayback Machine”. Disputatio, (II): 89–114.
- Hegedüs, Ramón, Åkesson, Susanne; Wehner, Rüdiger and Horváth, Gábor. 2007. “Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies”. Proc. R. Soc. A 463 (2080): 1081–1095
Other References
- Allen, Curtis. Primary Xray Analysis of Bronze. Keywell Metals, Stallings, NC USA, 2025.
- Dubin, Lois Sherr. The History of Beads. Harry N. Abrams Inc, 1993.
- HL Renart (the fox) of Berwick, “Glass Beads of the Viking Age”, https://dragonslaire.antir.org/wordpress/wp-content/uploads/2019/08/Viking_Beads_research.pdf