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Geosciences LibreTexts

3.2: Activity 3A- Assessing Hardness Values of Minerals

  • Page ID
    14516
  • Materials Needed

    • Mineral kit, provided by your instructor. This will likely contain numbered samples.
    • Hardness kit:
    • Your fingernail
    • A copper penny, plate or wire
    • Glass plate or knife blade
    • Steel nail
    • Hand lens or magnifying glass (at minimum 10x). How do I use a hand lens? Hold it very close to your eye and bring the sample near the lens until it is in focus.

    Recall, hardness is the scratching resistance of a mineral. You will need to determine if the mineral is harder or softer than the common material (Table 3.1). Use greater than (>) or less than (<) symbols to indicate the approximate hardness. For example, if your fingernail scratches your sample, look and feel for a gouge or groove in the sample, this sample would represent a hardness value of less than 2.5 (H<2.5).

    Table 3.1: Mohs Hardness Scale is a relative hardness scale, where 1 represents a soft mineral, like talc, and 10 represents a hard mineral, like diamond. ​

    Hardness number

    Mineral

    Test kit item

    10 (hardest)

    Diamond

    9

    Corundum

    8

    Topaz

    8.5 - Masonry drill bit

    7

    Quartz

    6

    Feldspar

    6.5 - Steel nail

    5

    Apatite

    5.5 - Glass plate or knife blade

    4

    Fluorite

    3

    Calcite

    3.5 – Copper (penny, plate, or wire)

    2

    Gypsum

    2.5 - fingernail

    1 (softest)

    Talc

    Your instructor will indicate which three minerals to assess for this section. Use Table 3.1 for guidance.

    1. Sample number:

    1. Does your fingernail scratch this sample? YES NO

    1. Does your sample scratch the copper or penny? YES NO

    1. Does your sample scratch the glass? YES NO

    1. Sample number:

    1. Does your fingernail scratch this sample? YES NO

    1. Does your sample scratch the copper or penny? YES NO

    1. Does your sample scratch the glass? YES NO

    1. Sample number:

    1. Does your fingernail scratch this sample? YES NO

    1. Does your sample scratch the copper or penny? YES NO

    1. Does your sample scratch the glass? YES NO

    Attributions

    • Table 3.1: “Mohs Hardness Scale” (CC-BY 4.0; Chloe Branciforte, own work)