Properties of Properties of MineralsMinerals

Geologists use characteristics Geologists use characteristics to tell one mineral from to tell one mineral from

anotheranotherColor / Luster / Hardness Color / Luster / Hardness

Break Patterns / Density / Special Break Patterns / Density / Special PropertiesProperties

I. I. ColorColorA.Not a reliable property for

identifying mineralsB.Examples: Quartz – smoky, rose, or

amethyst, Fluorite – many 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?

II. LusterII. LusterA. Refers to the way light reflects from

the surface of the mineral. B. There are two types of luster,

a. Metallic: looks like polished metal. b. Nonmetallic: does not look like

polished metal. i. Nonmetallic - Vitreous, Silky,

Resinous, Waxy, Pearly, Earthy

Pyrite has metallic Pyrite has metallic lusterluster

Quartz has nonmetallic Quartz has nonmetallic lusterluster

III. HardnessIII. HardnessA. A minerals

resistance to being scratched.

B. Friedrich Mohs German Mineralogist

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.

IV. Break PatternsIV. Break PatternsA. Cleaving – When minerals

break along flat surfacesB. Fracture – Some minerals

break unevenly along curved or irregular surfaces

C. Many types of fracture & cleaving

Quartz: Conchoidal Fracture Quartz: Conchoidal Fracture

Mica cleaves in one Mica cleaves 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.

V. StreakV. StreakA. The color of a minerals powderB. Minerals are scratched along a

streak plate to create powderC. Some minerals powder is a

different color from its regular color

D. Use both black and white plates

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.

VI. DensityVI. DensityA. Density – how much matter there is

in a given amount of spaceB. Density(g/cm^3) = mass(g) / volume

(cm^3)

Density of Platinum = 21.45 g/cm^3

VII. Special VII. Special propertiespropertiesA. Fluorescence – glow under

ultraviolet lightB. Optical propertiesC. Chemical reactionsD. TasteE. MagnetismF. Radioactivity