Description
The lens is slightly oval, and was roughly ground, perhaps on a lapidary wheel. It has a focal point about 11 centimetres (4.5 in) from the flat side, and a focal length of about 12 cm. This would make it equivalent to a 3× magnifying glass. The surface of the lens has twelve cavities that were opened during grinding, which would have contained naptha or some other fluid trapped in the raw crystal. The lens is said to be able to focus sunlight although the focus is far from perfect. Because the lens is made from natural rock crystal the material of the lens has not deteriorated significantly over time.
The Nimrud lens is on display in the British Museum.
Read more about this topic: Nimrud Lens
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