Science experiment using Rocks and Chocolate

This is the coolest Science experiment I have ever seen. I mean, teaching science, cooking and eating...how much better can ya get! I got this idea from my friend Heather P.'s blog and have been saving it just for this week!

You can illustrate the three different kinds of rocks by using chocolate.
Igneous rocks are formed from molten rock that cools.
Metamorphic rocks are rocks that have been changed by heat and/or pressure.
Sedimentary rocks are made up of bits of other rocks that have been transported by water, wind, ice or gravity.

How would you illustrate these categories with chocolate?

To simulate an igneous rock, make some fudge. You heat and stir the ingredients until they are completely melted. When it cools, it hardens into solid fudge, just as lava and magma cool into solid rocks.

For a metamorphic rock, bake some brownies. The heat of cooking causes a chemical change in the ingredients. What comes out is very different from what went in. That is very much like what happens to metamorphic rocks. Marble is not much like the limestone that it came from..

Since sedimentary rocks are made up of bits of other rocks, my first thought was to crumble the brownies. Instead of using water, wind or ice to transport the fragments, I decided to use gravity. Sprinkle the crumbled brownie into a bowl. Sedimentary rocks usually form layers, so make a nice layer of brownie fragments. Onelayer by itself is no fun, so let's make another one. Ice cream would represent anigneous rock, since it is cooled to make it a solid. Use a spoon to dig out chunks of the ice cream and let gravity deposit them on top of the fragments of metamorphic brownie. Keep adding fragments until you have a second layer. Now we have two layers of sedimentary rocks. How about a third layer? Chop some nuts very fine, to represent sand and gravel. Sprinkle a thin layer of the nuts to make the third layer. Now we have a very nice sedimentary example