Shipwreck find could be legendary sunstone
An oblong crystal found in the wreck of a 16th-century English warship is a sunstone, a near-mythical navigational aid said to have been used by Viking mariners, researchers say.
The stone is made of Iceland spar, a transparent, naturally-occurring calcite crystal that polarises light and can get a bearing on the Sun, they said on Wednesday.
It was found in the remains of a ship that had been dispatched to France in 1592 by Queen Elizabeth I as a precaution against a second Spanish Armada but foundered off the island of Alderney, in the Channel.
Shipwreck find could be legendary sunstone (http://news.ninemsn.com.au/technology/2013/03/06/12/29/shipwreck-find-could-be-legendary-sunstone)
A ready made navagation aid. Handy to know.
The stone is about the size of a small bar of soap whose edges have been trimmed at an angle. In technical terms, its shape is rhombohedral.
This is the natural shape for a relatively pure crystal of calcite.
How does the sunstone work?
If you put a dot on top of the crystal and look at it from below, two dots appear, because the light is "depolarised" and fractured along different axes.
You then rotate the crystal until the two points have exactly the same intensity or darkness.
"At that angle, the upward-facing surface of the crystal indicates the direction of the Sun," Ropars told AFP in an interview in 2011.
Survivalists and interested parties take note...
Quote Originally Posted by Umbuku
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Survivalists and interested parties take note
...please, not everyone at once!...