Mineral IdentificationMineral Identification

88thth Grade Earth Science Grade Earth Science

Dalton, Henry, O’RourkeDalton, Henry, O’Rourke

Physical propertiesPhysical properties

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

Mineral Identification KitMineral Identification Kit

ColorColor

Is the mineral light Is the mineral light colored or dark colored or dark colored? colored?

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

LusterLuster

How does the How does the mineral reflect light?mineral reflect light?

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

Luster (cont.)Luster (cont.)

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

Glassy Luster- Non-metallicGlassy Luster- Non-metallic

Pearly Luster – Non-metallicPearly Luster – Non-metallic

HardnessHardness

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

Hardness (cont.)Hardness (cont.)

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

Hardness of common objectsHardness of common objects::

Fingernail- 2.5Fingernail- 2.5

Copper Penny- 3.5 Copper Penny- 3.5 (1981 or older)(1981 or older)

Nail- 5.0Nail- 5.0

Glass- 5.5-6Glass- 5.5-6

Piece of steel- 6.5-7Piece of steel- 6.5-7

(like the head of a (like the head of a geologist’s hammer)geologist’s hammer)

Glass hardness platesGlass hardness plates

Cleavage/FractureCleavage/Fracture

CleavageCleavage- The - The mineral breaks into mineral breaks into layers along nice layers along nice flat edges.flat edges.

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

Cleavage/Fracture (cont)Cleavage/Fracture (cont)

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

Remember: Covalent bonds are Remember: Covalent bonds are weaker than ionic bonds.weaker than ionic bonds.

Cleavage/Fracture (Cont.)Cleavage/Fracture (Cont.)

FractureFracture- The - The mineral breaks with mineral breaks with rough jagged edges.rough jagged edges.

StreakStreak

Streak- colored powder left behind when a Streak- colored powder left behind when a mineral is rubbed on an unglazed porcelain mineral is rubbed on an unglazed porcelain plate.plate.This is similar to a teacher writing on a This is similar to a teacher writing on a chalkboard with a piece of chalk. The chalkboard with a piece of chalk. The chalkboard is harder than the chalk, so chalkboard is harder than the chalk, so pieces of the chalk are left behind and a pieces of the chalk are left behind and a “streak” is left on the chalkboard. “streak” is left on the chalkboard. Minerals with a hardness of greater than Minerals with a hardness of greater than seven will not leave a streak on an unglazed seven will not leave a streak on an unglazed porcelain plate.porcelain plate.

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

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

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

DensityDensity

DensityDensity- Typically, we do not measure the - Typically, we do not measure the actual density of a mineral sample in 8th actual density of a mineral sample in 8th grade science class, but density if a property grade science class, but density if a property used to identify minerals.used to identify minerals.A simple A simple HEFTHEFT test can be conducted to see test can be conducted to see if the mineral is more or less dense than if the mineral is more or less dense than typical objects of that size. typical objects of that size. If you are going to calculate the actual If you are going to calculate the actual density of the mineral, you would use the density of the mineral, you would use the formula, Density= mass/volume.formula, Density= mass/volume.

Special PropertiesSpecial Properties

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

Magnetite is magnetic.Magnetite is magnetic.

Fluorite and Calcite glow under Fluorite and Calcite glow under an ultraviolet light.an ultraviolet light.

Halite tastes like salt.Halite tastes like salt.

Sulfur smells like rotten eggs.Sulfur smells like rotten eggs.

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