Optical calcite is one of the most interesting specimens I've run across. It has an optical effect, it can have lovely rainbows, it's used even today in scienctific instruments, the Vikings used it to navigate the world, and it's cool!

It is called "optical" calcite because of its double-vision characteristic, as you can see by the finger below.

This optical characteristic makes it uniquely useful in the creation of high-tech instruments. At least one of YayBeads' specimens has gone to work in this way! Thinly sliced, but for a noble cause.

Another unique thing about optical is that it cleaves in a parallelogram, not a perfect cube or square. The shapes are simply broken along the calcite's natural lines and edges. The natural edges can be very sharp and flaky. While YayBeads' optical calcites aren't cut, they are polished.

One of the most amazing things about optical calcite, however, is their place in history. Optical calcite, also referred to as Icelandic Spar, was known to the ancient Vikings as the "Sunstone". It's remarkable optical features were used by the Vikings to find the position of the sun, even in cloud and fog*. It was their version of a compass and helped them to be the first to navigate to the East Coast of the United States!**

What exactly the Viking sunstone was and how it worked was lost in the mists of time until a sunken British ship off the USA coast was discovered to have one of these optical calcites in the wreckage, still in its ornate box. Treasure hunter and scientists agreed that it must be a valuable piece of equipment to be stored such.

Eventually they figured out how to use the optical characteristics to determine the direction of the sun, but why would a British ship with a compass need an Icelandic spar? It turns out that cannon are often magnetized and could throw a magnetic compass off by a few degrees. On a long voyage, that could be disastrous, so they apparently carried the optical calcite for back up!

This discovery was only made a few years ago and it's fascinating to read about if you want to do some Googling!

Most optical calcite specimens are small and milky from occlusions. YayBeads hand selects optical calcites that are typically larger and either exceptionally clear, or with vibrant internal rainbows. Either way, they make an awesome and conversation-starting specimen. Take a look at the real thing! http://yaybeads.indiemade.com/catalog/specimens-and-crystals

 

 

 

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* http://news.discovery.com/earth/navigating-by-sunstone-and-a-sixth-sense.htm

** http://worldnewsdailyreport.com/usa-ruins-of-viking-settlement-discovered-near-hudson-river/

Comments

The shapes are just broken

The shapes are just broken along the calcite's characteristic lines and edges. The characteristic edges can be sharp and flaky. While YayBeads' optical calcites aren't cut, they are cleaned. A standout amongst the most astonishing things about optical calcite, be that as it may, is their place ever. Optical calcite, additionally alluded to as Icelandic Spar, was referred to the old Vikings as the "Sunstone". It's astounding optical highlights were utilized by the Vikings to discover the position of the sun, even in cloud and haze

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