Pleasant Bay Pebbles 8 – At Pleasant Bay in Cape Breton Island, Nova Scotia, Canada, on the Cabot Trail in the Cape Breton Highlands National Park, the village sits on Carboniferous limestone rocks but the pebbles on its beach are mostly composed of much older igneous and metamorphic rocks that have been washed down from the surrounding mountains.
Jessica's Nature Blog 
Survival of the fittest…….limestone pebbles are often absent, even thought limestone is the outcroping rock, as they are outcompeted by harder rocks containing quartz, such as sandstones and various igneous and metamorphic rocks. Practical Moh Scale
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Thank you for the information, Robert.
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