Ask Ellen: Why is this sand purple?

LAKETOWN TOWNSHIP, Mich. (WOOD) — The sand on the shores of Lake Michigan are typically tan. That’s why a strange pinkish-purple stretch caught one viewer’s eye when she saw it on Wednesday on the shores near Saugatuck.

Colored sand at Saugatuck State Park. (Courtesy Rachel Kay-Beth Ouderkirk)

A strip of black and purple sand lined the shore.

Colored sand at Saugatuck State Park. (Courtesy Rachel Kay-Beth Ouderkirk)
Colored sand at Saugatuck State Park. (Courtesy Rachel Kay-Beth Ouderkirk)

The secret to the sand has nothing to do with a chemical change or a type of algae. Instead, the sand is a result of something we’ve seen a lot of lately: erosion.

The purple flakes are made of garnet, which is a deep purple. Most of the Great Lakes basin is composed of sandstone, which is tan. This gives our sand beaches their tan hue. However, there are strips of garnet that are embedded within the sandstone all over the Great Lakes.

When one of these layers is eroded, flakes of garnet enter the lake and can be pushed up on shore, making the purple sand. Often, this can create strips of black sand, too, where darker deposits are eroded and thrown on shore.

Colored sand at Saugatuck State Park. (Courtesy Rachel Kay-Beth Ouderkirk)

Occasionally, the purple sand mixes with the tan sand to make for a “pink” look. That is exactly what happened in 2017 at Pictured Rocks National Lakeshore.

Since we are home to a living lakeshore, these strips of purple won’t stick around forever, so enjoy them when you find them peppered on one of your favorite beaches on our Great Lake.

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