Robert A Whit
03-11-2013, 04:13 PM
There are good technical write ups for those interested but let me sort of summarize then show you some Iceland spar that has some remarkable properties.
The story goes that if you take a piece of the same mineral that Iceland spar is, and carve a groove in it such that when you stare into the grove, that only when the polished faces of the groove are lined up with the sun correctly, one sees two images that can then be lined up. This is is told is how vessels on the ocean once were able to use the sun to track by.
Some of these crystals will just be transparent. You can look at some that have double images when put over print. One has a so called rainbow making it glow.
Check it out. I happened to be looking at an article speaking of a piece of Iceland Spar being found in poor shape on a ship that sunk in the 1500's.
46714672
The story goes that if you take a piece of the same mineral that Iceland spar is, and carve a groove in it such that when you stare into the grove, that only when the polished faces of the groove are lined up with the sun correctly, one sees two images that can then be lined up. This is is told is how vessels on the ocean once were able to use the sun to track by.
Some of these crystals will just be transparent. You can look at some that have double images when put over print. One has a so called rainbow making it glow.
Check it out. I happened to be looking at an article speaking of a piece of Iceland Spar being found in poor shape on a ship that sunk in the 1500's.
46714672