Mineral identification
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Mineral Identification. 8 th Grade Earth Science Dalton, Henry, O’Rourke. Physical properties. To identify unknown minerals, scientists test various physical properties of the minerals using lots of different tools. Mineral Identification Kit. Color.

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Mineral Identification

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Mineral Identification

8th Grade Earth Science

Dalton, Henry, O’Rourke


Physical properties

  • To identify unknown minerals, scientists test various physical properties of the minerals using lots of different tools.


Mineral Identification Kit


Color

  • Is the mineral light colored or dark colored?

  • (The actual color of the mineral is important, but is not a characteristic that alone can be used to identify a mineral. Several minerals are the same color.)


Luster

  • How does the mineral reflect light?

  • Metallic Luster (Reflects light like a piece of metal)


Luster (cont.)

  • Non-Metallic Luster (Has a dull, pearly, silky, or glassy surface that does not reflect light.)


Glassy Luster- Non-metallic


Pearly Luster – Non-metallic


Hardness

  • Since glass has a hardness of 5.5, if we first test the mineral to see if it will scratch glass, we can eliminate all minerals either above it or below it on the Moh’s hardness scale.


After testing to see if the mineral will scratch glass, we can then test and determine the actual hardness of the mineral.

Hardness of common objects:

Fingernail- 2.5

Copper Penny- 3.5 (1981 or older)

Nail- 5.0

Glass- 5.5-6

Piece of steel- 6.5-7

(like the head of a geologist’s hammer)

Hardness (cont.)


Glass hardness plates


Cleavage/Fracture

  • Cleavage- The mineral breaks into layers along nice flat edges.


Mica is a mineral that breaks into layers. It shows cleavage.


Cleavage/Fracture (cont)

  • Cleavage occurs because the atomic bonds are weaker in that direction.

  • Remember: Covalent bonds are weaker than ionic bonds.


Cleavage/Fracture (Cont.)

  • Fracture- The mineral breaks with rough jagged edges.


Streak

  • Streak- colored powder left behind when a mineral is rubbed on an unglazed porcelain plate.

  • This is similar to a teacher writing on a chalkboard with a piece of chalk. The chalkboard is harder than the chalk, so pieces of the chalk are left behind and a “streak” is left on the chalkboard.

  • Minerals with a hardness of greater than seven will not leave a streak on an unglazed porcelain plate.


Streak plates are used to test the color of a minerals streak.

  • The dark colored plate is used for mineral with light colored streak.

  • The white plate is used for minerals with dark colored streaks.


Density

  • Density- Typically, we do not measure the actual density of a mineral sample in 8th grade science class, but density if a property used to identify minerals.

  • A simple HEFT test can be conducted to see if the mineral is more or less dense than typical objects of that size.

  • If you are going to calculate the actual density of the mineral, you would use the formula, Density= mass/volume.


Special Properties

  • Special Properties- Some minerals have special properties that make them very easy to identify.


Magnetite is magnetic.


Fluorite and Calcite glow under an ultraviolet light.


Halite tastes like salt.


Sulfur smells like rotten eggs.


Calcite fizzes when treated with hydrochloric acid. (Chemical Property)


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