Diamonds on the Souls of Our Shores: The Story of Fire Island Sand

Photo courtesy of Buzz Bragg.

By Emma Boskovski ~ Garnet is the birthstone of January. The wine rose colored stone also happens to be the official gem of New York State. Perhaps, most amazingly, Fire Island’s beaches are covered in it. It comes up right between our toes as we walk the shores, and we may hardly even notice it. Yet with each kiss of crashing waves, different minerals are deposited along the shore, which create the unique sand of Fire Island. We often think of the white sanded seashore that Fire Island offers, but sometimes we notice dark, dirty looking sand appearing in parallel patches that is often warmer to the touch. This shift in color signals a change in sediment, and that sand is not “dirty” at all, much of this is garnet, just like the kind you might see on a ring crafted by a jeweler. That is just the beginning of this open treasure. According to Fire Island National Seashore (FINS), the light colored sand is composed most commonly of quartz. Quartz is a clear to tan, translucent mineral that varies in size across Fire Island. Similar to quartz, feldspar is white to tan and appears opaque. Feldspar is not as common as quartz but contributes to the mostly white appearance of our sand. The dynamic tidal action can shred shells into particles small enough to contribute to sand composition as well, similar to how rock erosion creates particles of sand. This portion of sand does not necessarily contribute to the light sand in the same way quartz and feldspar do, but is much of what you see when grains of darker pigment come into the mix. As the lightweight quartz, feldspar, and shell are carried by powerful winds, darker patches of sand below may be exposed. Unlike light colored sand, dark colored sand patches are composed of high density minerals like garnet, staurolite, magnetite, ilmenite, and hornblende. According to FINS, garnet appears to be a light pink or reddish tone and is a translucent mineral – pulverized semi-precious stone. The dark sand soup also includes staurolite, a dark orange to red mineral that is translucent. Garnet and staurolite are often confused for one another during sand mineral identification because of their immense similarity in color darkness.Some magnetic minerals exist along our shore as well, easily identifiable when separated by levels of magnetism despite their striking visual similarities. Magnetite is a dark metallic color and is the most magnetic mineral found in Fire Island’s sand. Ilmenite is weakly magnetic and appears as an iron-black to steel-gray mineral. Hornblende is the darkest mineral of all appearing in the sand, as a black opaque mineral, and is the least magnetic of the three .Beaches are most dynamic along the shoreline as sand is constantly re-deposited because of both crashing waves and longshore transport. According to a project led by the New York Sea Grant Extension Program, the amount of sand transported depends on the size and frequency of the waves and currents.Further up the beach lies what is known as the berm, says FINS. This sand is often untouched by the water as it is outside the tide’s grasp. The berm is often white in clear conditions, and darker when windy. British poet William Blake once wrote: “To see a world in a grain of sand and heaven in a wild flower Hold infinity in the palm of your hand and eternity in an hour.” His words still hold true. 

Shoshanna McCollum also contributed to this article.