Iceland spar (crystal)
Iceland spar is a transparent birefringent calcite or also Icelandic limestone (crystallized calcium carbonate). (Note: crystal generally will be described in other post…). It became well-known because of the Vikings who used it as “sun-stone”, capable to determine position of the Sun at even completely overcast sky and capable to do so with an accuracy of one percent; it even works when the Sun is below horizon. This is possible due to physical phenomenon – polarization of light – which is used for navigation also by some animals (eg. bees); functionality was proved for example by an experiment of a team of physicists under guidance of Mr. Guy Ropars. So, the stone was probably used as an aid to navigate ships. It is therefore possible that long before invention of a compass, this kind of crystal could help the Vikings discover shores of America. This mineral is often found in Scandinavia and in addition it allows easy processing to required diamond shape. For comparison, magnetic compasses were fully implemented as navigation tool in late 16th century, although the first mention of them is already from turn of the 12th and 13th centuries. Archaeologists found Icelandic spar at approximate size of a cigarette box on ship that sank around 1592 near Norman island of Alderney near France. This would confirm theory of Danish archaeologist Thorkild Ramskou, who came up with the specific idea of using this “sun-stone” in 1967. Unfortunately we do not have more pieces of clear archaeological evidence; one possible reason is the fact that the Vikings often used cremations for funerals and any sun stone as part of grave items had no chance to preserve as one piece. Similarly, other minerals – cordierite and tourmaline – could work in similar way. Outside of North Europe, this kind of crystal is mined in the USA, Mexico and China.
This mysterious “sólarsteinn” appears in written sources eg. in a short allegorical story “Rauðúlfs þáttr” from the 12th or 13th century, which is about Saint Olaf (king of Norway in the years 995 – 1030) and his visit of a certain wise man, their evening together and what the king dreamt of during the night; before the king leaves in the morning, the man’s son Sigurd (Sigurður) shows him how to use sunstone although there is cloudy sky. Furthermore, the “sólarsteinn” is also mentioned in another saga, “Hrafns Sveinbjarnarsonar saga”, which is a part of so called Skálholtsbók written probably in the 15th century; here it is rather an allegory. Further, the sunstone is mentioned in other Icelandic written sources (eg. the churches and monastery inventory from 14th-15th century).