Several students have expressed interest in creating their own mock rocks at home; what a great way to review concepts that are being taught in class! You can increase your child’s understanding and interest in earth materials by asking him or her to talk about (or teach/lead you through) the investigations we are doing at school. Rocks, which appear so commonplace, may become objects that inspire questions and promote close observation. You and your child may want to start a rock collection, or visit the library or (if possible) a rock and mineral display to expand your rock and mineral knowledge. A visit to a landscape materials center or a jewelry store (gems are minerals) can expose the broad range of uses for earth materials.
We will continue to investigate a selection of the most common rocks and minerals that make up Earth’s crust, and learn more techniques used by geologists to identify them. Geology requires analysis. To develop these analytical skills and techniques, we first took apart a simulated rock called a Mock Rock (what I've included the recipe for). We observed them, broke them apart, dissolved them in water, and evaporated the liquid to discover the ingredients from which our rocks are made. We have now moved on to real rocks and minerals, using scratch tools and acid (vinegar) to test for specific minerals.
Next week we will look at granite, the base rock from which continents are made, and analyze it to discover the minerals it contains.
Enjoy! ( :
250 ml (1 cup) white flour
125 ml (1/2 cup) salt
10 ml (2 tsp.) alum
125 ml (1/2 cup) water
5 drops red food coloring
5 drops blue food coloring
3 drops yellow food coloring
250 ml (1 cup) coarse sand
125 ml (1/2 cup) gravel, 2 colors
30 ml (1/8 cup) oyster-shell pieces
• Bowl or large zip bag
• Stirring spoon
• Measuring utensils
• Tray, cookie sheet, or plates
• Paper towels
(Makes 18 5-cm rocks)
MOCK ROCK RECIPE
Make mock rocks 1 WEEK BEFORE starting the activity. Allow them to air dry to become hard.
MAKE THE MOCK ROCKS
1. Mix the flour, salt, and alum in the bowl or large zip bag.
2. Add the food coloring to the 1/2 cup of water.
3. Add the colored water to the flour mixture. Knead the mixture until it is uniform in color and texture and no longer sticks to the side of the bag or bowl. (Add a little more water if the dough is crumbly.)
4. Add the sand and the gravel to the mixture and knead until it is well mixed.
5. Divide the mixture into 18 balls, varying in size. Hold a rock ball in the palm of your hand, and with your thumb make a small hole in the center. Place 10–12 pieces of oyster shell in the hole and mold the dough around them.
6. Work the ball of dough in your hands, smoothing its surface. Flatten the rock so that it is 1– 2 cm thick. (Thinner rocks dry more quickly.) Create a set of rocks that vary in size and shape by making each rock a little different.
7. Put the rocks on a plate or tray. Make sure the rocks do not touch each other. Place them in a warm area to dry. Turn them each day so they will dry thoroughly. It takes them about a week to dry, depending on the humidity.
NOTE: Do not put rocks in a microwave or electric oven; they get much too hard. Drying time can be reduced by placing the rocks in a traditional gas oven. Don't turn on the oven. The heat from the pilot light will dry the rocks in 24 hours.
8. Use a paper towel to wipe the sand and gravel pieces from the utensils so that the solid materials do not go down the drain.
Mrs. Ana Rhyne
I teach 4th grade math and science at Weatherstone Elementary School. I graduated from Meredith College with a BA in Spanish and K-6 licensure.