How do we know?
↻ One of the pages with a moving picture
Scientists look at sand grains up close.
- Most sand starts as rock, often thousands of miles from the ocean.
- Bits travel down rivers and streams, breaking smaller along the way.
- At the coast, waves and tides wear them down into sand.
- Bits of shells and coral can mix in too.
Scientists study grains up close. Some sand turns out to be the tiny shells of one-celled sea life called foraminifera!
Different beaches have different sand. The green sand beach in Hawaii gets its color from a green mineral called olivine. White Sands in New Mexico is the world’s largest field of gypsum dunes, some 60 feet tall.
And some sand comes out of fish. One bumphead parrotfish can make hundreds of pounds of white sand a year, as poop!
Wow number
Hundreds of pounds of white sand a year can come out of one bumphead parrotfish. Yes, as poop!
Myth or fact?
Black sand is made of coal. Myth. It comes from worn-down lava rock near volcanoes.
Most beach sand is tan because of iron oxide, a kind of rust. Fact. It tints the grains light brown.
Think about it
Where did the sand in a sandbox start out?
Where in the world?
Green Sand Beach, Hawaiʻi where the grains get their color from a green mineral. White Sands in New Mexico is the world’s largest field of gypsum dunes — 18.9366° N, 155.6465° W.
Where these facts come from
Every number on page 27, and who measured it
This page explains where sand comes from, and about the parrotfish.
How does sand form? — NOAA's Ocean Service, U.S. ocean scientists
oceanservice.noaa.gov/facts/sand.html
We checked it on 31 October 2026
This page tells us sand starts as rock far away.
Coastal Sediments—Parent Material (U.S. National Park Service) — The U.S. National Park Service
nps.gov/articles/coastal-sediments-parent-material.htm
We checked it on 31 October 2026
This page tells us about Hawai'i's green sand beach.
Eruptions of Hawaiian Volcanoes [USGS] — The U.S. Geological Survey, the government's Earth scientists
pubs.usgs.gov/gip/hawaii/page36.html
We checked it on 31 October 2026
This page tells us about the giant white dunes at White Sands.
NPS Geodiversity Atlas—White Sands National Park, New Mexico (U.S. National Park Service) — The U.S. National Park Service
nps.gov/articles/nps-geodiversity-atlas-white-sands-national-monument.htm
We checked it on 31 October 2026
Has this changed?
Where sand comes from is not going to change.
Sand keeps being made right now, as waves and rivers wear rock down.
Words from this page
- coral
- A tiny sea animal. Many of them together build hard reefs, and their bits can become sand.
- foraminifera
- One-celled sea life with tiny shells.
- olivine
- A green mineral that gives some sand its color.
Try it!
Be a sand detective.
1. Sprinkle sand on dark paper. 2. Look with a magnifying glass. 3. Sort grains by color. Wash hands after.
Look: can you find clear grains, dark grains and tiny bits of shell?
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