In a small paper cup pour 3 tsp. Water and 2 TBLS. of Faster Plaster. Have the Brownies stir with popsicle sticks for two minutes. Next have the Brownies stir in sand and pebbles. Let cups stand for 10 -15 minutes. Add a piece of craft wire in the center ( if it does not stay up add it 3 to 5 minutes later, or hold up with a twisty tie until firm). If firm enough have the Brownies add shells, glass, etc on top. Set aside to harden – approximately 10 minutes. Bend the top of the wire into several small tight circles. Slip a photo in between wire.
Brownies are to take the picture holders home.

This experiment demonstrates one way in which rocks are formed. The three types of rock to discuss with the Brownies are:

Sedimentary: Created from layers of sediment which over time and with pressure bind together. These layers can include organic matter such as plants and shells.
Examples: Limestone, sandstone, shale

Metamorphic: means “to change.” This rock is formed when heat and pressure are applied.
Examples: Limestone + heat + pressure = Marble
Shale + heat + pressure = Slate

Igneous: means “fire”. This is rock which has been melted and cooled changing the rocks structure.
Examples: Basalt, Obsidian, Granite, Pumice

National Engineers Week Foundation
1420 King Street   Alexandria, VA 22314
tel. 703.684.2852   email: eweek@nspe.org