DID - YOU - KNOW
ICELAND SPAR
AND HOW IT CHANGED THE WORLD

By: Angel Mayes
Iceland Spar, is probably the most important substance ever mined.  It was originally thought that Iceland Spar was only deposited in Helgustadir, Iceland, hence the name, buried within the basalt flows where the spar may have an origin. Iceland Spar contributed to the Vikings who used this mineral to find America, was the key to discovering what light actually was, optics from Huygens, to Newton, to Fresnel, and even Edwin Land (of Polaroid fame), and contributed to wining World War II.
Are you wondering just what is Iceland Spar?  It is a crystal of calcite (calcium carbonate).  It is unique among the calcites as it has no impurities, so it’s nearly colorless and transparent to both visible and ultraviolet light.  Calcite is a fairly common mineral and comes in a spectacular range of colors caused by different mineral composition.  There are three types of calcite the most abundant type is white calcite, next is the clear, colorless calcite from which is culled and trimmed hence the optical “Spar” and third type is a banded pink calcite.  Both pink and clear spar mineral composition consist of manganese and magnesium. This brings the question why is the Iceland Spar not colored?  Scientist speculate the clear spar is composed of manganese and magnesium where in addition the pink has presence of silicon and aluminum thus providing color to the calcite.   
According to legend, Scandinavian warriors (Vikings) used a mythic tool to navigate the rough northern seas called a “sunstone”.  The sunstone was first discovered from a wreckage of a 16th century ship and was used to pinpoint the sun even when it was veiled by dense clouds and fog.  By 1967, archaeologist speculated that these legendary stones were actually crystals – possibly cordierite or Iceland spar, the material acted as a natural polarizing filter.  The warriors pointed she sunstone skyward and by rotating it until sunlight passed through it they were able to locate the sun for navigation. 
When the United States entered World War II the military needed accurate gun sights for warplanes and anti-aircraft guns.  Aerial gun sights of the time were large bulky prisms and lenses.  Edwin Land, invented the optical ring sight, which consisted of two sheets of polarizing film, invented by Land in 1928, and two optical wave plates sandwiching a crustal of Iceland spar. Iceland spar soon became a considered a strategic resource by the U.S. government. 
Iceland spar refracts light into two separate images giving way to polarization, this phenomena turned the world upside down in the 1600s.  Through several theorist including Isaac Newton, came the development and understanding of wave theory of light that explained polarization. Once there was a solid understanding it wasn’t long before scientist put the polarization theory with Iceland spar to good use, they developed polarized microscopes, analyzed atmospheric conditions, developed optic glass and lenses, and even attempted to use Iceland spar to create 3-D imaging. 
Iceland Spar, may go down in history as the most valuable mineral known to man worldwide.


References:
Iceland Spar: The Rock That Discovered Optics, Internet source.
Iceland Spar Is Produced in New Mexico, Roswell Daily Record January 29, 1942, courtesy of the Historical Museum for Southeast New Mexico.
Iceland Spar in New Mexico, Vincent C. Kelley, University of New Mexico Volume 25, pages 357-367 1940.
Evidence of Fabled Viking Navigational Tool Found, By:  Jennie Cohen 2013.