Whether it’s white, black, pink, red, or even green, the color of sand provides clues as to its makeup and offers a peek into the beach’s history. The color of sand can tell stories of past human activity and can even reveal what kind of sea creatures call that beach home.
Sand’s color is derived from its mineralogy, or the physical structure of the crystals that populate the sand. These minerals can come from erosion of nearby landscape, volcanic eruptions, and even the grounding up of sea shells over decades, so the color and content of sand reflect the makeup of the surrounding landscape and even the beach’s inhabitants.
So how do sand beaches around the world get their colors? Let’s take a look at how some of the world’s most colorful beaches came to be.
What Causes Sand to Be White?
White sand beaches are some of the most striking to look at, so striking in fact you’ll need to wear sunglasses to withstand the glare. Hyams Beach in New South Wales, Australia, is on record as the whitest sand beach on Earth according to the Guiness Book of World Records. The sand owes its bright white color to the purity of its content which is mostly finely ground quartz crystals with a lack of contaminants that could dull its color. Clearwater Beach on the Florida barrier island between Tampa and the Gulf of Mexico and the beaches on Angaga Island in the Maldives also host strikingly white sand beaches composed of a finely ground powder of quartz.
What Causes Sand to Be Red?
Red sand beaches, like those that cover much of Prince Edward Island in Canada, including Cavendish Beach, derive their color from iron-rich minerals. When iron comes into contact with oxygen it forms iron oxide or what we more familiarly call rust. This oxidation leaves the minerals looking different shades of red and is the same process at work in the rust-colored, iron-rich dust on Mars.
A volcanic cinder cone, a simple, single-vent volcano, surrounds the Kaihalulu Beach in Maui supplying it with iron-rich minerals and thus red sand. Similarly, the iron-rich black and red lava rocks have produced the Kokkini Beach, known as Red Sand Beach, nestled into the base of the nearby volcanic cliffs of Santorini, Greece.
What Causes Sand to Be Orange?
Minerals high in iron can also produce sand with an orange hue as seen on the beaches of Ramla Bay in Gozo, Malta, and in Porto Covo, Portugal. Similarly, the orange sands in Porto Ferro in Sardinia, Italy, come from a combination of orange limestone, crushed shells, and volcanic deposits.
What Causes Sand to Be Pink?
When a beach has pink sand, some form of coral is usually nearby. The shade of pink usually reveals a mixture of white sand with red shells or calcium carbonate from coral and thus can range from pastel to deeper pinks. The famous pink sand beaches on Harbour Island in the Bahamas are composed of ground up foraminifera, a single-celled marine organism with a red-colored shell. The beaches in Balos, Crete, also get their pink hue from crushed shells. In Tangis Beach in Indonesia and the Rangiroa Atoll in French Polynesia, white sand is mixed with red coral to produce pink sand.
What Causes Sand to Be Purple?
The Pfeiffer Beach tucked between the ocean and the Los Padres National Forest in Big Sur, California, boasts unusual purple-hued sand. The sand gets its color from a mineral called manganese garnet which is found in the hills that surround the beach. Rain in the area causes erosion which washes the manganese garnet down toward the ocean. The beach is not uniformly purple and the erosion runoff can create swirled patterns of colored sand. To see the beach at its most purple, visit just after a winter storm has sped up the erosion process.
Large swatches of purple sand are also found on Plum Island Beach off the eastern coast of the United States. On Plum Island, home to seals, raptors, and snowy owls, the purple sand results from a mixture of fine grain pink sand with darker grains. The pink sand crystals are mostly made of almandine-pyrope garnet, a common mineral derived from metamorphic rocks in the area. Some of the darker grains even include green epidote, another mineral common in metamorphic rock.
What Causes Sand to Be Black?
Black sand beaches, like Punalu’u Beach in Hawaii, get their color from basalt, a common igneous rock that forms as lava cools. In Hawaii, underwater volcanic vents spew magma which cools rapidly when it meets the ocean water. The resulting chunks of basalt then wash up on shore to cover the beach in grains of black sand.
If you are looking for more than one color in your beach sand, the Rainbow Beach in Queensland, Australia.
Past volcanic activity has also created the Black Sand Beach in Vik, Iceland, and the Muriwai Black Sand Beach in Auckland, New Zealand, thanks to a mixture of basalt deposits, iron, titanium, and other volcanic material. The black sand on Playa Negra in Puerto Viejo, Costa Rica, also has the fun, added quality of being magnetic thanks to its iron content.
What Causes Sand to Be Green?
The mineral olivine is responsible for the beautiful but rare green sand beaches, like Papakolea Beach on the big island of Hawaii. Olivine is another mineral that, like basalt, forms as lava cools. The olivine at Papakolea was deposited there by the Pu’u Mahana cinder cone, part of a now-dormant volcano whose magma was rich in olivine. The clash of hot lava and cold ocean water also produce the olivine-rich green sand beaches in Kourou, French Guiana.
If you are looking for more than one color in your beach sand, the Rainbow Beach in Queensland, Australia, offers sand with what some say are more than 70 different colors derived from erosion of nearby, multi-colored cliffs. And not all sand colors are natural in origin. Two beaches known as Glass Beach, one along the southern shore of Kauai and the other near Fort Bragg, California, also boast a rainbow of colors but are entirely human-made. The multi-colored sea glass that makes up the “sand” on both beaches may be gorgeous to look at but comes from glass pulled out to sea from industrial-sized garbage dumps nearby and smoothed by ocean waves over decades.
Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.
Image courtesy of shutterstock.
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