Lesson 2 - Page 2


PROBLEM: How can you distinguish different minerals?


Earth Science - Minerals, streak plate (included in kit). HCl (dilute), steel nail, periodic table, small piece of quartz (included in kit)

Look at your mineral specimens and answer the following questions.

  1. FLUORITE is made up of calcium fluoride (CaF2) which usually grows in cubic crystals. It breaks into 8 different faces to give a diamond look (octahedral cleavage). Fluorite can be found in many colors, and can be scratched by a steel knife. Fluorite is a common mineral, that is found all around the world. In the United States the best known location is in southern Illinois and northern Kentucky. Fluorite is used in making steel, in decorative glass, in enameling cooking utensils, and for hydrofluoric acid. The name comes from the Latin fluere, meaning to flow since is melts easier than other minerals.  
    1. Look at the 2 types of fluorite. Describe their shape.

  1. The pieces of both types of fluorite have been broken. When a mineral breaks into smooth surfaces this is called "cleavage." What word do you think cleave is derived from? Explain.

  1.  What do the two specimens have in common?

  1. Fluorite is calcium fluorite. What elements make up fluorite? (Hint: use your periodic table)

  1. Is fluorite harder or softer than quartz?

  1. How can you tell?

  1. Do you think color is a key characteristic of fluorite? Why?

  1. BORNITE (Cu5FeS4) is a copper ore that rarely is found in crystal form. Bornite is usually found associated with other copper minerals. Bornite when exposed to the atmosphere will tarnish blue to purple. It's primary use is as an ore of copper. Bornite is named after the German mineralogist von Born.   
    1. Bornite is a copper compound that is called the "peacock ore." Why is bornite called the peacock mineral?

  1. Bornite chemical composition is Cu5FeS4. Write out the elements that are in Bornite. Can you guess why it makes this "tarnish" color?


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