What is sand made of?

From a distance, the sandy beach looks like a large golden land next to the sea. However, if you take out a microscope to look at the sand, a whole new world will appear. In particular, the ingredients that make up the sand beaches are also extremely rich, some of the ingredients revealed below may surprise you!

As rivers flow downstream, the flowing water erodes the rock into tiny grains of rock, while carrying these small pieces of rock with them. Along the river’s journey, the pebbles continue to be worn down, eventually becoming sand as the river flows into the sea.

When rivers flow into the ocean, sand is deposited along the land. The waves constantly shift the deposited sand of the river, creating beautiful shorelines.

Sand will look slightly different in different parts of the world, depending on the type of rock eroded by the river.

Brown and yellow sand is usually made up of feldspar – a quartz-like iron oxide mineral that gives it a golden brown color. The darker black sand is caused by basalt, which is formed from volcanic activity. This type of sand is often found in oceanic crust or where there are many active volcanoes, such as the islands of Hawaii.

The image below shows sand from Hawaii under a microscope. The green gravel is a mineral called Olivin, a mineral derived from volcanic basalt rock. The black spots in the picture are basalt. Hawaii has many active volcanoes, which explains why this sand is found there.

What is sand made of?
The sand on a Hawaiian beach under a microscope, the green color is a mineral called Olivin.

The size of sand grains is determined by the degree of weathering. Fine sand grains mean they have been weathered for a longer time by water.

Studying the minerals in sand helps geologists know a lot about how landmasses form. For example, by studying basalt-rich sand in Hawaii, scientists can study the island’s origins and determine when and how the island formed.

Interestingly, desert sand also comes from the sand near the beaches. When waves hit the shore at an angle, it pulls sand at the beach, lengthening the coastline. However, sometimes the wind blows the sand inland, creating dunes.

In fact, sand is made up of the skeletons of many invertebrates, such as clams, corals, and other sea-dwelling shellfish. Waves bring them to shore, where they settle. These objects erode very slowly, making it difficult to become finer sand.

There are several other organisms that contribute to sand around the world. For example, the foraminifera produces pink beaches in Bermuda. Pinworms are single-celled shellfish that live in the ocean. Some species of foraminifera are red, which gives Bermuda’s sand a pink hue.

What is sand made of?
Pink sand at Horseshoe Bay beach in Bermuda

These red hole worms live near coral reefs in Bermuda. When they die, their red-shelled skeletons are brought ashore, where they mix with white sand to create picturesque pink sands.

Sand is also made from manure. Yes, you heard that right… and more specifically parrot fish poop

Parrot fish are like cows of the sea. These colorful tropical fish spend almost 90% of their time eating corals, or rather, algae that grow on corals. They use their hard beak-like mouth to scrape and eat chunks of coral for their daily meals.

What is sand made of?
Two parrot fish enjoying their meal.

As the coral passes through the guts of the parrotfish, the algae in the coral will be digested, while the calcium carbonate rock that makes up the coral remains. Because parrot fish cannot digest calcium carbonate, it will excrete it as fine sand.

A large parrotfish can produce up to 450 kilograms (1,000 pounds) of calcium carbonate sand in a year. The ravishing white tropical beaches of Hawaii, the Maldives and the Caribbean are mostly formed from parrotfish droppings.

Although we can’t see it, sand also harbors a rich micro-ecosystem that is important for the health of large ecosystems and other interdependent ecosystems.

Algae is very common living on sand. These algae can photosynthesize and produce a variety of molecules (don’t forget oxygen from photosynthesis), becoming part of a healthy ecosystem. Many marine or coastal organisms depend on these algae, making them an important part of the food web.

Human waste can also form beaches. In 1949, the State of California began using the area that is now Glass Beach as a dumping ground for all kinds of garbage, from vehicles and food to pots and glass. Finally, after nearly 20 years, the authorities realized that dumping the trash there was not the best option and closed the area.

Gradually, a number of cleaning initiatives began to work on the beach. Toxic waste has been eliminated and biodegradable materials have been degraded. The water eroded the tiny pieces of glass and clay from the pots by rounding them and giving the beach a colorful effect.

What is sand made of?
Glass Beach in California.

Sand isn’t just here to make sandcastles or sunbathe… it’s also opening up new ways for us to see the world — and our place in it!