Curious to try to navigate like a Viking? This Optical calcite, or Iceland spar, will do that for you!
With sharp edges and smooth sides, this transparent rhombus is a beautiful example of optical calcite.
Calcite is one of the most common minerals on earth, being found all over the world in sedimentary, igneous and metamorphic rock. Iceland spar is clear and transparent forming in a natural rhombus due to the split along cleavage planes. Named for where it was first discovered, the best Iceland spar comes from Iceland where it is also most abundant. It is also found in Mexico, Brazil, China, and New Mexico, and can even come in colors like yellow and pink. It is famed for its double refraction, or "birefringence" -- one ray of light is split into two beams of polarized light, causing two images of different brightness when looking through it.
Recent research has led to the belief that Vikings once used Iceland spar when navigating over 1,000 years ago. Vikings utilized what they called "sunstones" to locate the position of the sun on cloudy days to then set their ships on course. They would rotate the spar until the brightness of each image become relatively equal, which can only occur when the calcite is inline with the sun (even during cloud cover). Iceland spar was used for gun sights in World War II and is used for telescopes, microscopes and cameras.
Size: ~ 1.63 x 1.25 x .94 inches
Weight: 2.15 oz. / 62 g.