Greensand
“Sand colored by the sea”
Greensand is a sedimentary rock or unconsolidated sediment colored green by the mineral glauconite, which forms on the sea floor under specific low-oxygen conditions. These distinctive green layers are found worldwide and serve as excellent time markers in the geological record.
glauconite, quartz, feldspar, calcite, clay minerals, phosphate
New Jersey Coastal Plain (USA), Weald (England), Paris Basin (France), Papahua Beach (New Zealand), Delaware (USA)
4-5
Greensand has been used as a natural fertilizer for over 200 years — the glauconite slowly releases potassium and iron into the soil, and George Washington reportedly used it at Mount Vernon.
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What specific marine conditions cause the mineral glauconite to form in greensand?
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