Thousands upon thousands of paired edible mussel shells lay semi-embedded in wet, rain-pitted sand at Whiteford in Gower. These shells often wash ashore and accumulate in dry piles along the strandlines from the natural mussel beds just offshore. On this occasion, unusually, the shells were trapped and scattered widely across the shore like so many petrifying blue butterflies stranded in the sediments.
Revision of a post first published 4 May 2010
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Jessica's Nature Blog 
Beautiful blues. They do look like butterflies in your photos. There is a large blue mussel bed at nearby Rainbow Haven Beach but I seldom see their shells on the beach. You seem to get so much thrown up on the shore in your part of the world.
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Mussels grow naturally and in great abundance in this area, settling on all sorts of substrates (even thin strands of seaweed) from which they are easily dislodged. This is great for the mussel gatherers who rake them up into sacks when the beds are exposed on very low tides. However, strong waves and stormy weather can tear them from their attachment. I have been told that on one occasion the mussel shells were knee deep on the strandline.
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