Introduction:

At this point you should have a good understanding of the rock cycle, the 3 main classifications of rocks (sedimentary, metamorphic, and igneous) and the forces/processes that change them. You should also have a basic understanding of the characteristics used to classify rocks within these groups (information contained in your rock notes).Now you are going to attempt to use that information to identify individual rock names.You might want to review Chapter 3.2-3.4 paying particular attention to the pictures and the classification tables.

Procedure:

  1. Choose one of the rocks. Observe its texture, color and crystal size. Record your observations in the data table.
  1. Use the key to rock classification table below to classify your rock. Begin by reading the first questions. Answer Yes or No based on your observations.
  1. After the words Yes or No, you will find directions to proceed to another question, or you will discover to which group of rocks your specimen belongs. If you find directions to proceed to another question, go to that question, answer it, and follow the directions.
  1. Continue working through the key in this way until you come to a statement that allows you to classify your sample rock.
  1. In Data Table 2, record the route that you take through the key, using the numbers of the questions. For example, your route could be “1—7—8—extrusive igneous rock.” In the second-to-last column of the table, write the name of the rock group to which each sample belongs.

Data Table 1:

1. Does the rock contain visible connecting crystals? / Yes: Go to question 2.(Hint: there should be 6 with and 6 without)
No: Go to question 7.
2. Are all of the crystals the same color and shape? / Yes: The rock is a nonfoliated metamorphic rock.Go to question 3.
No: Go to question4.
3. Does the rock have large crystals? / Yes: The rock is marble.
No: The rock is quartzite.
4. Are all of the crystals in a mixed "salt and pepper" pattern? / Yes: The rock is an intrusive igneous rock.Go to question 5.
No: The rock is a foliated metamorphic rock.Go to question 6.
5.Does the rock consist of more than 3 colors? / Yes: The rock is granite.
No: The rock is gabbro.
6. Does the rock have flat thin layers that have been pressed together? / Yes: The rock is schist.
No: The rock is gneiss.
7. Does the rock have flat thin layers that can be broken apart? / Yes: The rock is a sedimentary rock. The rock is shale.
No: Go to question 8.
8. Does the rock have a uniform dark color? / Yes: The rock is an extrusive igneous rock. Go to question 9.
No: Go to question 10.
9. Does the rock appear so dark it appears black (or very dark gray)? / Yes: The rock is basalt.
No: The rock is limestone.
10. Does the rock contain pebbles, sand, or smaller particles that are cemented together? / Yes: The rock is a clastic sedimentary rock. Go to question 11.
No: The rock is an extrusive igneous rock. The rock is rhyolite.
11. Does the rock contain larger pieces of rock? / Yes: The rock is conglomerate.
No: The rock is sandstone.

Data Table 2:

Sample / Description / Route to Identification / Type of Rock / Rock Name
1 / Basalt
2 / Gabbro
3 / Granite
4 / Rhyolite
5 / sandstone
6 / Limestone
7 / Shale
8 / Conglomerate
9 / Gneiss
10 / Quartzite
11 / Marble
12 / Schist

Analysis and Conclusions
1) Compare your results to one other person. Do their results support or not support yours? What was different?
2) How difficult was it to use the classification key and tables to identify your rocks? What problems did you encounter?
3) How useful was rock color in classifying the rock samples? Explain.
4) Which two rock samples were the easiest to identify? What properties made it easy?
5) Which two samples were hardest to identify? Why?