Rock Cycle - Minerals (6A)
Pre Lab 

   
OBJECTIVES:
  • Exploring the composition of minerals.
  • Distinguish elements that become positive or negative.
VOCABULARY:
  • charged
  • ions
  • mineralogy
  • negative
  • positive
MATERIALS:

Students study the chemical compositions of minerals.


Tiger eye, a form of quartz.

BACKGROUND:

A mineral is a naturally occurring, inorganic element or compound with a definite chemical composition, a characteristic crystalline structure, and distinct chemical properties. The study of minerals is called mineralogy. It includes mineral identification and description, the classification of mineral groups, and the study of mineral occurrences. 

Gems are substances that have economic and aesthetic value. Most gems are minerals. However; some gems are organic substances such as amber, while others are rocks. Professionals who specialize in the study of gems are called gemologists.

Crystal form is the natural shape a mineral takes when it grows into open space. Crystal form reflects the elemental composition and arrangement of atoms within the mineral. However, most gems are cut or faceted to make attractive gems.

PROCEDURE:
  1. Use the Gemstone worksheet to help students visualize gems as a combination of elements (compounds). The chart is arranged in "mineral families." Have the students find and list all the silicate minerals (containing Si and O).
     
  2. Instruct the students to list the other "mineral families" that are on the Gemstone worksheet. These include corundum, turquoise, diamond, and spinel. Ask the students what the minerals in each "family" have in common. Students should recognize that the last part of the chemical formula (the "suffix") is similar.
     
  3. Ask students to find the most common elements used in the front or prefix of the chemical formulas. Al (aluminum), Mg (magnesium), Fe (iron), K (potassium), and Ca (calcium) are most common.
     
  4. Students should  locate these elements on the periodic table. See if they can determine if there are any consistent differences between the positions of the "prefix" and "suffix" of how the elements are written. They should see that most of the "suffixes" are in the right side of the table, and the "prefixes" are mainly on the left. This reflects how the elements combine to make stable compounds. The minerals on the left tend to be positively charged, while those on the right are negatively charged. They combine to make stable compounds.
     
  5. Students should look at the different gems in the Gem  Kit, and see how many of them are on the Gemstone worksheet.

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