Several centuries underwater have rendered the alderney crystal opaque , but dr ropars and his team are now examining it , and believe it may be iceland spar .
A british island in the english channel . The northernmost of the larger channel islands , it is separated from the french coast by a swift channel , the race of alderney .
Though no sunstones have survived from viking days , despite the frequency of ship burials of viking chiefs , there is one tantalising find from a more recent shipwreck . This is a large calcite crystal recovered from a vessel that went down off the coast of alderney , in the channel islands , in elizabethan times .