Purple Amethyst
On a beach along the Ottawa River, I found purple sand. Could this be amethyst ?
The "purple sand" is about a foot wide and runs the length of the beach. It is about ten feet inwards from the water line. I have not had the chance to observe them under a microscope yet but I suspect amethyst. How did it come to gather in such a large concentration of fine particles ?
Some areas in and around the Ottawa River are rich in the minerals manganese almandine or spessartine garnet. Around a beach area, if these are present , the result will be purple sand.
"Most grains of sand are light, such as quartz, feldspar and muscovite. But a few, such as magnetite, ilmenite or garnet are dense minerals. That's the reason that after a storm you might see bands of hard purple sand — those are grains of almandine garnet. A buried scarp might contain 50 percent heavy minerals vs. less than 5 percent in the background sand."
http://www.townonline.com/falmouth/homepage/x566565559
Pfeiffer Beach in Big Sur is known for its purple sand. The further north you travel the more purple the sand. The surrounding hillsides are full of manganese garnet that get washed down.
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