Properties of Properties of MineralsMineralsGeologists use Geologists use

characteristics to tell characteristics to tell one mineral from one mineral from

anotheranother

Mineral Properties we will Mineral Properties we will studystudy

Luster Hardness

CleavageStreakDENSITY

Color

Fracture

ColorColor• Color is the first thing someone notices when

they view a mineral. • Color is also one of the big reasons that attract

people to minerals. • Generally speaking, color is not a good property

to be used in the identification of minerals. It is usually the first property to confuse a novice collector into making an incorrect identification.

• Many minerals have different colors and some minerals' colors are identical to other minerals' colors.

A mineral can be many A mineral can be many different colors. Below is Mica.different colors. Below is Mica.

Many minerals can be the same color. Many minerals can be the same color. Below are gold colored minerals. Which Below are gold colored minerals. Which

one is gold?one is gold?

The answer…The answer…None of them None of them

were real gold. were real gold.

LusterLuster•Refers to the way light reflects

from the surface of the mineral. •There are two types of luster,

–Metallic: looks like polished metal. –Nonmetallic: does not look like polished metal. •Nonmetallic can be shiny or dull.

Pyrite has metallic Pyrite has metallic lusterluster

Quartz has nonmetallic Quartz has nonmetallic lusterluster

StreakStreak• When a mineral is scratched along a

ceramic streak plate it may leave a specific streak of color.

• Red chalk on a chalk board makes red marks. White chalk makes white marks.

• Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.

GoldGold• When gold is

run across a streak plate it makes a yellowish-gold color.

• That makes sense.

Pyrite or “Fool’s Gold”Pyrite or “Fool’s Gold”• When pyrite is run

across a streak plate, it has a black or dark green streak.

• Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.

HematiteHematite• Hematite’s color is

grey, but its streak is red.

• Hema means blood. • The mineral was

named hematite because it looked like it was bleeding when it was taken across a streak plate.

When a mineral breaks it does so

either by fracturing or by

cleaving.

CleavageCleavage•The tendency of a mineral to

break along flat surfaces. •Some minerals split easily

along a flat surface. •Not all minerals have

cleavage.

Mica has cleavage in one Mica has cleavage in one direction. direction.

It breaks along one line. It breaks along one line.

Feldspar has two lines of Feldspar has two lines of cleavage. It breaks along cleavage. It breaks along

two lines. two lines.

FractureFracture•Fracture is the tendency of a

mineral to break into irregular pieces.

HardnessHardness• The resistance to being scratched. • Is measured by how easy it is to

scratch.• Geologists order the hardness by…

1. Scratched by a fingernail.2. Scratched by a penny. 3. Scratched by a nail. 4. Scratched by a diamond.

The Mohs Hardness Scale is used to identify a mineral’s hardness.

Gypsum is soft, it can be Gypsum is soft, it can be scratched by a fingernail.scratched by a fingernail.

Calcite is soft, but a little Calcite is soft, but a little harder because it cannot be harder because it cannot be

scratched by a fingernail, but it scratched by a fingernail, but it can be scratched by a penny. can be scratched by a penny.

Fluorite is harder. It can be Fluorite is harder. It can be scratched by a nail, but not a scratched by a nail, but not a

penny or fingernail. penny or fingernail.

Diamonds are the hardest Diamonds are the hardest mineral, so it scratches every mineral, so it scratches every

mineral. mineral.

DensityDensity• Each mineral has a specific density.• Density is the mass of a given

space or in scientific terms the mass per unit of volume.

• For example, if you have two minerals of the same size one might be heavier than the other. The galena will be three times heavier than the same size of quartz.

Special PropertiesSpecial Properties• Some minerals have specific

properties• Fluorescence: some minerals glow

when exposed to ultraviolet light• Magnetic: Some minerals are

attracted to magnets• Acid: Some minerals react with acid

by bubbling