Students will understand that sand is made up of different minerals-one being magnetite, a compound containing iron.
Sand at Great Sand Dunes is made up of a variety of minerals, as can be seen if you look closely at a pinch of sand. One of the more obvious and interesting components of the sand is magnetite, a mineral that has eroded out of the nearby Sangre de Cristo Mountains. This black mineral is composed of iron oxide, so magnets are able to pick it up.
Because magnetite is also very heavy, when the wind blows, the lighter weight sand is blown away, leaving magnetite behind in patches. These black patches can be seen in the dunefield from a distance.
Explore Great Sand Dunes' web pages on geology to learn more about the origin of the sand.
Hand lenses, pencils, magnets, small cups, white paper, sand
This activity will help students understand that sand at Great Sand Dunes is composed of different minerals. Have each student take a small pinch of sand and spread it on a piece of white paper. Look through a hand lens and describe the different grains by color and size. Have students write a list of all the colors of sand they see. Talk about sand coloration and how different minerals have different colors. Go to the park's Visitor Center to see the mineral exhibit.
Have students use a magnet to extract black grains of magnetite from their sample of sand. Explain that magnetite is heavier than most of the other sand grains in their sample. Point out that from a distance magnetite can be seen in the dunefield. Have them look at the sand dunes and take note where black areas of sand can be seen.
Find a flat surface and have students place some magnetite from their samples on a piece of white paper. Using a magnet, have each student make designs with the magnetite on the paper and share them with each other. Afterwards, return the sand to the dunes.
Note: if you are doing this activity on a windy day, check with a ranger about using the Visitor Center porch or another sheltered space. Remember, please don't remove any sand from the park.
Compare magnetite with other sand grains. Talk about how sand is based on size and not material (see All Sand Grains, Great and Small which talks about grain size and has a chart). Ask if anyone has ever been to the beach or another place with lots of sand. Have them describe what the sand there was like. Compare the different sandy locations.
Back in the classroom, have students research different uses of sand and share what they find with the class. Sand is used in many ways (i.e., sand blasting, filtration, sand paper, etc.).