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I recently started designing and making jewelry. I'm particularly fascinated by Iolite. [Iolite]("https://en.wikipedia.org/wiki/Cordierite" https://en.wikipedia
by will_walker 11y ago
I recently started designing and making jewelry. I'm particularly fascinated by Iolite. [Iolite]("https://en.wikipedia.org/wiki/Cordierite" https://en.wikipedia.org/wiki/Cordierite") is commonly referred to as "water sapphire" or "viking's compass". This is because it changes in tone depending on it's angle to the sun. Historically it would have been useful because the effect works regardless of cloud cover and even when the sun is below the horizon. I'm not sure if the nickname is a historic remainder or attached during modernity (the jewelry industry is both ancient and opaque) but the effect is real, and could potentially be of concrete utility during navigation.
- dalke 11y agoThis article says that the three likely possibilities for 'sunstone' (if it really was used for navigation) are calcite, tourmaline, and cordierite. It was Thorkild Ramskou who made this hypothesis in the 1960s. I strongly suspect it didn't gain the poetic moniker 'Viking's compass" until afterwards. Moreover, if it were used in the jewelry industry before the 1960s then it would be strong supporting evidence for the hypothesis.
- GeorgeRichard 11y ago"... it changes in tone depending on it's angle to the sun ... the effect works ... even when the sun is below the horizon." This sounds like magic. Have you observed this effect yourself and do you have an explanation for it or a reference to one?
- analog31 11y agoI'll have to check it out, next chance I get, with a polarizer. One thing that could be exploited is that the sunlight scattered by the ionosphere (why the sky is blue) is polarized, so the polarization axis could be the clue.
- dalke 11y agoAccording to your link, that's the case. It only works when the sun is just below the horizon so there is still scattered light in the sky.