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Geosciences LibreTexts

7.3: Lab Exercise (Part A)

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    5570
  • Materials

    Your HOL Lab Kit contains 18 numbered mineral samples, separated into 3 bags (labeled as Mineral Bag 1, 2, or 3). Use these instructions to test and identify them. You will test for different properties after learning about them, then work on identification at the end of the lab. The HOL kit has been specifically tailored to this class – make sure that you are using the kit required by this class, as other rock and mineral kits will not work. Images will be provided of the correct kit; make sure that you closely compare your kit to the images so that you are working with the correct samples. Empty the contents of the testing kit. It will contain:

    • A 3” copper wire
    • Glass plate (wrapped in paper) – this will be used in testing hardness
    • Zinc coated nail
    • Unglazed porcelain plate (wrapped in paper) – this will be used as a streak plate
    • Hydrochloric acid
    • Magnifying glass (10x). To use this, hold it very close to your eye and bring the sample near the glass until it is in focus (approximately one inch from your eye).
    • Gloves and protective goggles (for use with the acid)

    Take out Minerals Bag 1 and lay the six mineral samples out on a white sheet of paper. It should appear like Figure 7.8. We will first examine hardness from these six samples and will answer more questions about them later in the lab. Looking closely at each of the minerals, use the hand lens to observe them. In this bag, you have the following minerals (not listed in order): Microcline (also called Potassium Feldspar), Fluorite, Quartz, Olivine, Talc, and Selenite (also called Gypsum). They are numbered 1-6.

     

    You need to experiment with each sample to test for its hardness and use Figure 7.5 for reference. Remember that hardness is determined by scratching the mineral (or using the mineral to scratch something else). First, decide which minerals have a hardness greater than 5.5 (the hardness of glass). Lay the glass on a flat surface (not in your hand), then try to scratch it with each mineral. Bare down hard with the mineral, much like trying to leave a scratch on a car with a key. Table 7.1 is given at the end of this lab for you to make notations about each mineral. Note that you do not have to fill in every physical property for every mineral (that would be very time-consuming with 18 samples). Just fill in the properties you are asked about as you work. Note now on the table which minerals have a hardness greater than 5.5.

     

    You may also test samples by using materials to scratch them. The copper wire has a hardness of 3. Any mineral that it can scratch will have a hardness less than 3. You can further refine this by using your fingernail (only natural fingernails work for this). Your fingernail has a hardness of 2.5, so if the copper wire scratches a mineral and your fingernail also scratches it, you know its hardness must be <2.5. The zinc-coated nail has a hardness of 4. Also, use it to scratch the minerals. Minerals may also be used to scratch each other. For example, if you have two minerals that have a hardness of <2.5, you can see if one will scratch the other. Then, you know it is harder since it did the scratching.

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    Part A

    1. Sample 1: What is this sample’s hardness?

    a. harder than glass

    b. softer than glass but harder than nail

    c. softer than nail but harder than copper

    d. softer than copper but harder than a fingernail

    e. softer than a fingernail

     

    2. Sample 2: What is this sample’s hardness?

    a. harder than glass

    b. softer than glass but harder than nail

    c. softer than nail but harder than copper

    d. softer than copper but harder than a fingernail

    e. softer than a fingernail

     

    3. Sample 3: What is this sample’s hardness?

    a. harder than glass

    b. softer than glass but harder than nail

    c. softer than nail but harder than copper

    d. softer than copper but harder than a fingernail

    e. softer than a fingernail

     

    4. Sample 4: What is this sample’s hardness?

    a. harder than glass

    b. softer than glass but harder than nail

    c. softer than nail but harder than copper

    d. softer than copper but harder than a fingernail

    e. softer than a fingernail

     

    5. Sample 5: What is this sample’s hardness?

    a. harder than glass

    b. softer than glass but harder than nail

    c. softer than nail but harder than copper

    d. softer than copper but harder than a fingernail

    e. softer than a fingernail

     

    6. Sample 6: What is this sample’s hardness?

    a. harder than glass

    b. softer than glass but harder than nail

    c. softer than nail but harder than copper

    d. softer than copper but harder than a fingernail

    e. softer than a fingernail