The Finest Cabochon Gemstones in the World

The Crystal Blog


I recently read an interesting book called How to Catch a Robot Rat. The authors explain how for as long as there have been technological advancement, humans have modelled these advancements on nature. They go way back in history citing ancient ideas for robotics and bionics, and how they play out in the present. Well I found it interesting any way. In one section they discuss birds and how they navigate during migration using polarized light, and compared this to the Vikings and their use of a mineral called cordierite, which I had never heard of. But my interest was immediately peaked. It took very little research to find out that gem quality cordierite is in fact. Yes, you’ve guessed it, iolite.

Iolite is called the violet stone. Its colour ranges include blue, brown, yellow, dark violet, grey and green. But gem quality  iolite is generally violet blue colour. This gemstone also exhibits pleochroic qualities. Which means that the violet blue colour is visible, until the stone is turned through 90 degrees. Then it will display a more bluish brown colour. And then if that stone is turned on its side, it may display a completely new shade of blue or brown.

Iolite was also called the 'Vikings Compass'. Because the pleochroic effect works by determining the direction that light waves are traveling. Very useful for determining the suns position on overcast days. With a well polished piece of iolite and a good understanding of the way that the colours shift within stone, in relation to the sun, and you could theoretically navigate your way across the Atlantic. Regardless of the weather, as it's the polarization that affects the stone. Not the sun.

I have many beautiful gemstones and mineral specimens, which I consider to be prized possessions that I will never part with. But I am hard pushed to imagine a better reason for a prized position then that of a gemstone that helped to navigate to the new world, and back home again. Centuries before compasses, and Christopher Columbus.

[How to Catch a Robot Rat by Agnes Guillot, Jean-Arcady Meyer, Susan Emanuel (2010)]

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