I wrapped a natural optical calcite rectangle crystal with silver aluminum wire and added a 24 inch silver plated rope chain. Like most optical calcite specimens, it has rainbow prisms. This specimen is from Nuevo Leon, Mexico. It is pale green in color and fluoresces orange under UV light.
Green calcite is a good stone for achieving mental and emotional balance. It can create new energy pathways to release you from old patterns that may be keeping you from moving forward. It helps you to look at things from a different and more positive perspective. Green calcite is a peaceful crystal that manifests earth energy and is useful to those who work with plants.
Optical calcite is a good cleansing stone and can amplify environmental energy. It is also restorative and helps to accelerate psychic development and spiritual growth. It provides insight in negative situations and aids in clarification during confusing emotional states.
Iceland spar is the name often used for optical calcite because that is where the crystal was originally discovered. The supply from Iceland has been mostly depleted, due to the use of the calcite in scientific instruments in the 19th and 20th centuries, and also for its use in gun sights during World War II. Optical calcite is also found in other places such as the United States and South America, but Mexico and China is where much of it comes from now. Iceland spar is clear variety of calcite originally found in Iceland. It was often used in experiments involving light polarization, as it is well known for its double refraction qualities. It easily divides into rhomboid shapes. Some historians have speculated that it is the original sunstone mentioned in medieval texts (solarsteinn), that Vikings used to tell the direction of the sun on overcast days. An international team of researchers led by Guy Ropars of the University of Rennes in Brittany, marshalling experimental and theoretical evidence, says they have the answer. Vikings, they argue, used transparent calcite crystal -- also known as Iceland spar -- to fix the true bearing of the Sun, to within a single degree of accuracy. This naturally occurring stone has the capacity to "depolarise" light, filtering and fracturing it along different axes, the researchers explained. Here's how it works: "If you put a dot on top of the crystal and look through it from below, two dots will appear. Then you rotate the crystal until the two points have exactly the same intensity or darkness. At that angle, the upward-facing surface indicates the direction of the Sun," Ropars explained by phone. "A precision of a few degrees can be reached even under dark twilight conditions. Vikings would have been able to determine with precision the direction of the hidden Sun." He added, "The human eye has a fine-tuned capacity to distinguish between shades of contrast, and thus is able to see when the two spots are truly identical." Source: http://phys.org/news/2011-11-viking-sunstone-myth.html#jCp