OBJECTIVES
1. Identify rocks and relate them to their origins via the rock cycle
2. Investigate and chart some of the physical properties of rocks
3. Study current, historical and ancient human uses of rocks
4. Interpret data and plot geologic information on a base map

ACTIVITY—MAKE A ROCK:
   Create a sedimentary “rock” in the classroom by making daily layers in a clear plastic soda bottle (with top part cut off) or directly on newpaper. Try using the following: sand and glue, small pebbles and glue, pebbles and sand and glue, yard dirt. Make the glue from a thick sugar syrup (sugar dissolved in just a little water). After making each layer, let glue dry completely, at least overnight (you could punch small holes in container, heat gently on a hot plate, or just make your sediment cakes right on a newspaper). At the first reference to sedimentary processes during the unit, discuss this "rock" with the students. They may enjoy breaking up their “rock.” Students could place part of the rock in water, observing that it is the cement that dissolves, not the particles.
   There are some instructive analogies here. Clastic sedimentary rocks are made from sediment grains that are compacted and glued together with natural substances, especially calcium carbonate and silica. These “glues” were dissolved in groundwater and later precipitated between sediment grains, hardening the sediment into rock.

INTRODUCTION TO THE WORK STATIONS:
   Individual teachers introduce the unit by presenting igneous, sedimentary and metamorphic rocks, using large specimens and slide sets and passing out bags of smaller rocks and magnifiers. Gather or purchase the supplies; then introduce each of the following work stations, through which the students can circulate in groups during each of the next four days.

WORK STATION ONE: ROCKS AND THEIR ORIGINS
Learning Objectives:
   The student should learn to organize rocks according to primary and secondary origins: igneous (intrusive or extrusive), sedimentary (clastic or non-clastic), metamorphic (foliated or non-foliated). Each of the secondary types is important for understanding plutons, vocanoes, and the key varieties of sedimentary and metamorphic rocks and environments. The student should learn to recognize and identify at least two rocks in each secondary category (2 intrusive, 2 extrusive, etc.). Using the Rock Cycle, she should understand the origins of each rock type and the way rocks relate to each other. She will know where and under what environmental conditions each type of rock forms.
   Nature Science recommends learning the following 18 rocks. These represent all the key types, including 6 of each primary type and 3 of each secondary type. Most of earth’s rocks are either one of these 18 or a close relative.

EXTRUSIVE -grains too small to see
4. Rhyolite: light pastel color, often mottled. May be soft. May contain visible crystals.
5. Andesite: intermediate shades between rhyolite and basalt. Often dotted with visible crystals.
6. Basalt: gray or black. May have holes (vesicles). May turn rust red.

NON-CLASTIC -transported as dissolved chemicals (ions in solution)
10. Limestone: soft, light to dark gray, fizzes with acid, grains visible or too small to see.
11. Chert: very hard, edges sharp, looks like porcelain, may be almost any color.
12. Gypsum: clear or white, very soft (scratch with fingernail).

NON-FOLIATED -little or no layering
16. Quartzite: looks like sandstone but harder, smoother and more sparkle (sugary texture).
17. Marble: soft, sparkly interlocking grains. Usually white or pastel shades. Fizzes with acid.
18. Metaconglomerate: may contain stretched or flattened pebbles. May be foliated.

Required Materials (available from Nature Science Collections):
1. Collection of rocks including examples of all three primary types and, if possible, at least two or three examples in each secondary type
2. Copies of rock identification chart, rock cycle and rock origins chart below
3. Small unmarked specimens of each rock type
4. Rock and geology books explaining rock identification and origins
5. Students' science notebooks

Activities:
At this station, students examine all the specimens in the collection and, using the charts and materials provided, sort out the ones labeled igneous, sedimentary, and metamorphic and the secondary types (extrusive, clastic, etc.). They will notice the differences in appearance, texture or “feel”, and weight in the groups of rocks. In their notebooks, students can list the names and categories of all the rocks. They may choose their “Favorite Rock” and write a brief report on it, using books provided. Students may then copy the rock cycle into their notebooks. Students work alone or together to identify each small unmarked specimen and, using the Rock Origins chart, place each specimen on the chart near the correct environment for that rock. Finally, students may also write the name of each rock in its appropriate place on the Rock Origins chart, and place the chart in their notebooks.
 

WORK STATION TWO: PHYSICAL PROPERTIES OF ROCKS
Learning Objectives:
   Students physically test rock samples for color, texture, hardness, and reaction to dilute acid, and chart their findings. More advanced students may add weight or specific gravity, luster, cleavage, and transparency/opacity.
Required Materials:
1. Small, unmarked rock specimens
2. Scratching implements including fingernail or plastic spoon (2½), penny (3), screwdriver or metal implement (5½), quartz specimen (7). Hardness scale indicated in parentheses. Or use a hardness test kit.
3. Full strength vinegar or diluted pool acid (10% muriatic or hydrochloric)—mix by pouring one part acid into nine parts water (not vice-versa)
4. Copies of Physical Properties chart, or help students make their own
5. Student notebooks
Activities:
   Using a self-created Physical Properties chart (example below), students fill in results of their investigations of color, texture, hardness, and reaction to acid.
 

WORK STATION THREE: USES OF ROCKS
Learning Objectives:
   The student will do personal research, using books and materials provided, to explore the present-day and ancient uses of rocks in various cultures. Then they will make a creation from rocks.
Required Materials:
1. A collection of books, pamphlets, or other information about rocks and their uses in world culture and history
2. Science notebooks
3. Materials for making creative rock project
Activities:
   Students research written or media materials provided and write brief reports on interesting uses of rocks. There are many ways to organize this. They could do a longer report on one feature such as the Egyptian or Aztec pyramids, the Great Wall of China, or an architectural feature such as Machu Picchu, a Roman aquaduct or the Acropolis. Or they could do a paragraph on each of five or ten different rock types and their modern and ancient uses. Some students may want to do a report on rocks as weapons (catapult, slingshot, arrowhead) or on uses of rocks in body paint or jewelry. Students may also provide bibliographic entries for their references according to a pre-taught bibliographic format.
   Students work together or individually to create artistic rock projects according to their own or teachers’ guidelines. Ideas include pet rocks, rock sculptures, a model rock wall or house, a small Japanese-style rock garden, a sand painting, a table-top fountain (see Nature Science Collections) for the classroom, or other creative project. It may be a good idea to have students bring their own rocks to school for this. Teacher might emphasize ordinary rocks rather than valuable mineral specimens.
Evaluation:
  Teacher evaluation of grammar, spelling, accuracy, completeness, creativity, information in students' own words, and bibliographic entries. Students may evaluate their own rock creations using criteria suggested by teacher.

WORK STATION FOUR: GEOLOGIC MAP OF ARIZONA

Learning Objectives:
   Students will locate each of their rocks on a simplified geologic map of Arizona (or home state) and color the geologic map using that data. This process will provide a review of rock identification and knowledge of rock categories.
Required Materials:
1. Sets of large and small rock specimens (each large rock specimen should have a number affixed)
2. Handout: simplified geologic map of Arizona.
3. Colored pencils, pens or crayons
4. Actual full-sized geologic map of home state, available from state geological surveys, libraries, or universities
5. Student notebooks
Activities:
   Students find rock specimens that correspond to each number on the geologic map, using numbers affixed to rock specimens (the same munbers listed on the Identification Chart above). Students may place small specimens on the map according to the numbers. Using this information, they will determine the rock type (igneous extrusive, igneous intrusive, sedimentary clastic, sedimentary nonclastic, metamorphic, surface soil) for each area of the map.
   Using six different colors (one color for each different rock type plus surface soil) students mark their chosen colors in the squares of the explanation box at lower left. Then they fill in each area of the map itself with its corresponding color. Organizational and cognitive skills: the various numbers in a certain area of the map represent several different rock species but all of these will be of a certain primary or secondary type that they have learned, such as igneous extrusive, which includes rhyolite(4), andesite(5) and basalt(6).
Evaluation:
   The teacher can check the students’ geologic maps for neatness, completeness and accuracy. Geologic maps, with their bright colors, are often beautiful as well as instructive (and impressive!). Students may enjoy displaying their efforts.
 
Suggestion about Geologic Maps
   If your school does not have a rock collection, the geologic map will require you to use the same numbers (as on rock chart above in work station one) to number your rocks, or you could change the numbers to those you may have applied to your own rocks.
   If there is no simplified map of your state available, the teacher can make one. Get the complex “official” map, reduce its size, and trace it, simplifying the information. For example, you would take all the volcanic (extrusive) rock areas on the map and combine them into just a few larger map areas in approximately the correct map locations. Be sure you have numbered your rock specimens. On your map, place igneous extrusive rock specimen numbers in your combined igneous extrusive area(s). Do the same for the other rock types you wish to teach. Voila! Many states do not have all the rock types--you may then choose to use the Arizona map, as Arizona is a geologically diverse state. Again, the Arizona map is available free from Nature Science Company.

UNIT EVALUATION
   If you like, have the students evaluate the entire unit by completing a short questionnaire: “What I liked about this unit was ___ but here is what I would change next time: ___.” A hands-on style quiz might be appropriate. Some students may actually enjoy showing off their rock identification knowledge.