Properties of RocksProperties of RocksLesson 1Lesson 1

What you will learn todayWhat you will learn today

• What the wordsWhat the words homogeneoushomogeneous and and heterogeneousheterogeneous mean mean

• What makes a rock a rockWhat makes a rock a rock

Homogeneous mineralsHomogeneous minerals

• They have a They have a unique crystallineunique crystalline structure and structure and specific hardnessspecific hardness-just -just like this close-up of sandstonelike this close-up of sandstone

See the crystals?

What does Heterogeneous What does Heterogeneous Mean?Mean?

• Rocks are a made up of Rocks are a made up of more than more than oneone mineral. mineral.

FeldsparMicaQuartz Granite+ + =

Properties of RocksProperties of RocksThere are There are fivefive properties which help properties which help

identify rocks:identify rocks:

Hardness

Luster

Color

Streak

Density

HardnessHardness

200 years ago 200 years ago Friedrich MohsFriedrich Mohs devised a scale by which the devised a scale by which the hardness of minerals could be hardness of minerals could be ranked from ranked from 1 to 10.1 to 10.

ROCK JOKE

What is a rock’s favorite transportation?

A rocket!

At the high end (10) Mohs put the At the high end (10) Mohs put the hardest mineral, the diamondhardest mineral, the diamond

At the low end (1) Mohs put talc At the low end (1) Mohs put talc which is the softest mineralwhich is the softest mineral

How To Test HardnessHow To Test Hardness

• The hardness of a mineral can be The hardness of a mineral can be tested by doing a scratch testtested by doing a scratch test

• Many minerals do not go higherMany minerals do not go higher than 7 or 8than 7 or 8

Hardness ScaleHardness Scale• If your fingernail easily scratches the If your fingernail easily scratches the

mineral, it is a 1mineral, it is a 1

If glass can scratch the mineral, it If glass can scratch the mineral, it is a 5is a 5

If quartz can scratch the mineral If quartz can scratch the mineral it is a 7it is a 7

LusterLusterDescribes the Describes the appearance of the mineral’s appearance of the mineral’s

surfacesurface

Is it shiny?Is it dull?

Is it waxy?

Is it glassy?

Describes characteristics of Describes characteristics of color color and color combinationsand color combinations

StreakStreakStreak describes the Streak describes the color left by the color left by the

rockrock when drawn across hard when drawn across hard surfacesurface

This type of test helps when trying This type of test helps when trying to identify dark looking minerals.to identify dark looking minerals.

DensityDensityDescribes the Describes the weightweight of the rock. of the rock.

Gold has a density of 19

Talc has a density of 2.7

The density of water is 1

What does homogeneous mean?

What does heterogeneous mean?

What are the 5 properties of a rock?

Thanks goes to:

Sues’ Gemstones for the diamond pictures

Intel for creating a microscope that hooks into the computer for the close up pictures