Activity 1.2 - Review of Minerals and Rocks

• Differentiate between rocks and minerals, including rock-forming processes and rock families
• Draw concept maps to organize material learned.

A short class discussion about the reading will help clarify the concepts covered. Students will first discuss minerals and then complete a concept map to summarize the mineral and rock concepts learned in Unit 1.

Part 1. Reviewing the definition of a mineral:

1a) Ask students for the definition of a mineral. List the five criteria on the board.

1b) To practice using this definition, the instructor should ask students if a given substance is or is not a mineral. This can be done by starting a list on the board, titled "Mineral or Not?" If the five characteristics are also displayed, then the instructor can go through them for each substance, to see if that substance does or does not meet the criteria. For example, the instructor could write "plastic" on the list and, after brief discussion, write "No - is not natural" next to the word.

The following substances provide good examples of what minerals are and are not:

• Plastic is not a mineral because it is not natural.
• Wood (or bone) is not a mineral because it is not inorganic.
• Salt is a mineral. When going through the list, students should note that salt is solid, inorganic, and natural. Some will state that it is chemically homogeneous. The instructor can ask, "How do you know?" and then prompt, "What do all salt grains taste like?" Students should know that all salt tastes like salt, which is a clue that all salt shares the same chemical formula (NaCl). Some will state that the mineral is crystalline. The instructor can ask, "How do you know?" and then prompt "What does salt look like?" Some students probably have observed that all salt grains are little cubes. This is because of the crystalline nature of salt; the atoms are arranged in orderly and repeating cubes, and therefore salt breaks into cubes.
• Sugar all tastes the same and breaks into cubes, but sugar is not a mineral because it is not inorganic.
• Ice is a mineral. When going through the list, students should note that ice is inorganic and natural. Students will note that ice is solid unless it melts. This is a good place to note that all minerals can melt, and if they melt then they are no longer minerals. Ice is chemically homogeneous (with formula H₂O) and is crystalline. To stress this last point, ask students what snowflakes look like. Photomicrographs of snowflakes from http://www.its.caltech.edu/~atomic/snowcrystals/ can be used to show students that snowflakes are crystals, perfect and symmetrical, indicative of their crystalline nature.
• Coal is not a mineral. Students may not know how coal forms but can be told that coal forms from dead plants that cannot decay. Thus, coal is organic.
• Glass is not a mineral. Students might say that glass is not natural, until they are reminded of natural glasses like obsidian (which forms in volcanoes). Glass is not a mineral because the atoms are not arranged in an ordered and repeating pattern. Glass is not crystalline.

Part 2. Reviewing the definition of a rock, the three rock families, and learning how to work with concept maps:

This Partially Completed Concept Map in PowerPoint (PowerPoint 212kB Sep26 13) or in PDF (Acrobat (PDF) 147kB Feb11 15) should be distributed to students to help students (a) learn how to work with concept maps and (b) organize the concepts addressed so far in the reading and in class.

A Completed Concept Map. (PowerPoint 207kB Sep26 13)

After they complete the concept map, ask students: The concept map includes some things from the reading, but not everything. A good amount of the reading dealt with properties that make minerals useful. Where would "useful properties" fit on this concept map? What were those properties?

• This activity could be completed before or after the Minerals and Products matching activity.

More information about Concept Maps

Photos of snow crystals taken by Dr. Kenneth G. Libbrecht at CalTech: http://www.its.caltech.edu/~atomic/snowcrystals/.