PANNING FOR GOLD AND MAGNETITE

Eleanora I. Robbins and John P. D'Agostino
U.S. Geological Survey
National Center MS 956
Reston, VA 22092


Level: Elementary school


Anticipated Learning Outcomes


Materials Needed: IN FIELD

CAUTION: Ask about known allergies and ask permission to spray children against poison ivy or poison oak. Tell children what these plants look like (three leaves; central leaflet has a longer stem; sometimes, the leaves are reddish and glossy; one poison ivy variety climbs trees, and another is on the ground; the big hairy vines seen climbing trees are the other variety.) It has been discovered that the aluminum chlorhydrate in antiperspirants will stop poson ivy rash. Best use is to spray the antiperspirant on legs and rub between fingers. Have children wash their hands when they get back to school, and tell them to wash really well when they get home and to take their clothes off inside out so as not to infect the person who does the laundry.


Materials Needed: AT SCHOOL

Procedures

  1. Go to a stream that is not moving very fast.
  2. Fill the pan not quite full of different sizes of sediment: gravel, sand, and silt.
  3. Walk into the stream just until the water comes to the top of their shoes.
  4. Face downstream, which is the direction the water flows.
  5. Tilt the pan so it faces slightly upstream.
  6. Ask students to predict which sediment will wash out first and which will remain. Knead the sediment with your hands to thoroughly soak it and to wash out the clay.
  7. Shake the pan a little.
  8. Knead and shake, knead and shake, knead and shake, knead and shake to wash out the silt and light (usually white) mineral grains. The light minerals are the ones that come to the surface when you shake the pan. The heavy minerals are the ones that stay on the bottom of the pan.
  9. Keep pushing out of the pan all of the rocks, twigs, and light colored minerals. When only heavy minerals (usually the black grains) remain in the pan, pour out the water slowly, and then push the minerals out of the pan onto the newspaper to dry.
  10. Let the concentrate dry in the sun for approximately 15 minutes.
  11. After the concentrate is dry, put the magnet under the paper, and move all the magnetite away into a separate pile. Does your stream contain magnetite? How much of the concentrate is magnetite? What color is it?
  12. Look with the magnifying lens for gold in the minerals that remain behind. If gold is present, it will be as tiny flakes. Is gold present? What color is it? What is the color of the other heavy minerals?
  13. Label the plastic bag with the name and the location of the stream, mix the minerals back together again, pour them into the bag, and stick the magnet outside the bag so it is attached to the magnetite inside the bag and does not get lost. Is there enough magnetite in the stream to hold the magnet?
  14. Back at school, separate out the magnetite by using the same procedure as step 11 and weigh the magnetic and nonmagnetic fractions. Which is heavier? Look more carefully at the other minerals. How many different colors do you see?
  15. Gold is a soft metal, softer than most other metals. How can you test if a mineral is gold? Try a metal probe. Gold has different colors because it mixes with different impurities. Yellow gold is very, very heavy and will be with the gravel. Black gold is very heavy and will be with the sand. White gold is heavy and will be with the silt.


Discussion

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