After recording those two properties, we brainstormed as many different properties as we could that we could use to tell two rocks apart. The winning table group in our little competition identified seven different properties, most of them being used by geologists every day in their field research.
I took photos of all the rocks we had in our kit – nine in total. You are only responsible for taking observations on the first five, but you may find the others interesting. They aren't going to be the same as examining them in person, but it may give you enough information to take some general observations for the next investigation. I will provide some basic descriptions here as well.
You can click on any of the images to enlarge them.
Rock 1: Basalt
Greenish-brown or gray in color, the rock has very small grains of varying but similar colors.
Rock 2: Granite
Multi-colored with large grain sizes. Colors from black to white to pink to brown were seen in this rock.
Rock 3: Obsidian
Glassy, shiny black rock with sharp edges. There were no grains visible at all.
Rock 4: Gabbro
This rock was predominantly green and black with brown and deep yellow colors mixed in. The grains were large – perhaps larger than those in the granite sample.
Rock 5: Rhyolite
This rock had mixed grain sizes ranging from large to very small. The rock had varying colors from predominantly brown and tan to green and black.
Rock 6: Pumice (floating)
This rock was very unique and fascinated most of the students. It was very light, filled with pockets of air, rough to the touch, and brittle. It had very small grains and was very light tan in color.
Rock 7: Pumice (glassy)
This rock seemed very much like the pumice above, yet didn't have the air pockets and wasn't quite as light. It seemed to have layers, but the grains ranged from small to medium. The color was variable as well, compared to the floating pumice. It seemed to have a lot of variety.
Very light, but not full of obvious air pockets like the pumice. This had mixed grain sizes: There were medium to small black grains that could be seen, very crystal-like, but the majority of the rock was a lighter tan grain size that was very small.
Rock 9: Breccia
This rock had small to mixed grain sizes and samples had very different appearances: some were lighter in color, while others were darker. There was also inconsistency in the grains, from their color to their size, although no really large grains.
