Black Sand On Delaware Beaches

Why is the sand black?

Every coastal storm erodes the beaches, stirring and shifting the sand. The amount of sand that moves around is huge in some areas. Dark streaks or large patches of black sand collect along the beaches’ surface. It freaks people out, but it is supposed to be there. A combination of dense minerals such as, magnetite, and garnet create a purple, black or reddish sand. Also known as Iron Sand. Heavier particles than the typical sand settles on the top as the lighter sand washes out. Eventually it will cover over again.

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Black Sand magnified 1200 times on a microscope.

Use a magnet on the black sand, the magnetite will stick. There are also very tiny diamonds in that black sand. Not typical Delaware diamonds, but real diamonds.

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The “black sand” is heavier than the usual beige colored sand and is always under the beige, sandy beach. Sand “layers” according to a grain’s size and weight. Storms will disrupt the layers (erosion) and that process (layering) starts all over with the black sand exposed for a bit until the beaches recover.
You will find more of the black sand on the Delaware Bay beaches and the north pocket of the Indian River Inlet. Since it is heavier it collects in the north pocket as that area scours constantly like a bowl.

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Magnetite or Black Sand also know as Iron Sand. Separated out by a magnet.



If you look at the sides of the natural dunes that are scarped, or cut off like a ledge. There are layers (thin lines) of black sand. The wind pushes that sand around between storms and layers it in dunes at times. Natural dune building.

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