On December 2 the members of Bervie and District Probus were treated to a fascinating illustrated talk on Scottish Gemstones by Helen Plumb.
Scottish geology is well understood but is said to be more complex than any other country of comparable size in the world. Unusual gems are still being discovered in the ice scoured paths where the ice sheets ripped the overburden to the Atlantic Ocean and North Sea.
Scottish river pearls are an organic gemstone produced by a biological process by the fresh water mussel and is made of calcium carbonate deposited in concentric layers.
They are formed inside the shell of the mussel as a defence mechanism against a potentially threatening irritant such as a parasite or other alien object.
Although hundreds of Scottish rivers used to support colonies of the mussels, polution and overfishing contributed to their demise but they can still be found in the fast flowing, clod, clean water of the rivers Tay, Dee, Ythan and Feugh.
In 1967 William Abernethy found a pearl 12 1/2 mm in diameter. This is the largest pearl found in Scotland and was sold by him for £9000. After many questions expertly answered the vote of thanks was proposed by Gordon Mercer.