3-1 What is a mineral?3-2 Identifying minerals?

(epsomite)

{enrich} What is a Mineral? More than 4,000 minerals (40-50 new minerals

identified each year!) but only 100 common minerals about 20 minerals make up most of Earth’s crust native elements occur in nature in pure form (ex:

gold, copper, diamond, sulfur, graphite, silver, and platinum)

Most minerals are COMPOUNDS… (a chemical combination of two or more elements), while rocks are mixtures of minerals (and sometimes organic matter like shells)

Some minerals are elements (like copper, gold and diamonds)

{enrich} Classification of minerals

95% of the earth’s crust is made of silicates (minerals made of silicon and oxygen): ex: quartz SiO2)

sulfide (+ sulfur) ex: cinnabar (HgS)

sulfate (+sulfur & O)

carbonate (C & O) ex: calcite: CaCO3

oxide (+oxygen) ex: corundum: Al2O3

halide –ex: salt

Characteristics of ALL minerals: (INSCC)--foldable--

Inorganic Natural Solid Compound (or

element) Crystal system

Inorganic– never alive– not from

something alive– rocks can have

organic matter

Naturally occurring– not synthetic or

artificial or man-made

Solid– at room temperature

Chemical composition– some single element

in pure form (native elements) like copper, diamond, sulfur

– most are compounds like quartz (SiO2) and cinnabar (HgS)

– rocks are mixtures– Can you read a

chemical equation?

Crystal system– repeating pattern

with flat sides (called faces)

– most are only visible with a microscope

8 ways to test the identify of a mineral

1--hardness 2--color 3--streak color 4--luster

5--density 6--crystal structure 7--cleavage/fracture 8--special properties

Hardness how easy is it to scratch the mineral? Moh’s scale

– 1812 by Friedrich Mohs– 1 (talc) - 10 scale (diamond)– common substances:

fingernail=2.5 penny=3-3.5 glass=5.5-6 steel=5-5.5 streak plate=

6.5-7.5

Colors of QUARTZ

Two colors

Color– easy but not reliable– color may change over

time– some minerals have

MANY colors (like quartz)--due to impurities

– many minerals have the same color

Streak Color--practice– more reliable than

regular color– color of its powder– use streak plate

(unglazed tile)– examples:

pyrite=black gold=golden, yellow

Luster– how a mineral

reflects light from its surface

– 1. metallic (shiny)– 2. nonmetallic:

glassy, dull, earthy, waxy, pearly

Density– mass/volume– remains the same (no

matter the specimen size)

– also called “heft”– may use “specific

gravity” (same as density, but no units)

Types of luster

Crystal System– Example: cubic-– Example:

hexagonal

Cleavage/Fracture (paper towel demo)– how a mineral BREAKS – 1. Cleavage=smooth break– 2. Fracture=irregular break—

rough, jagged, or curved (most minerals have fracture) quartz=curved, shell-like surface copper and iron=hacky fracture

(forms jagged points)

Special Properties

Fluorescence (glow under UV light)--scheelite

magnetic--magnitite radioactive--uraninite fizzes (gives off CO2)

in acid– calcite (demo)

Very malleable (easy to shape)--gold

earthy odor--clay soapy feeling--talc feels greasy--graphite double refraction--

optical calcite

Special Properties:

A rock is a mixture of _____________. minerals

Mystery mineral game:

Pick a mineral from pp. 800-801 other classmates must ask yes/no questions

to determine the identity of the mystery mineral (like “20 Questions)

LAB: What mineral do you have?

Find color and streak color What is the luster? Find the hardness (a range) Find density (use water displacement for volume)

—could use “heft” AFTER 2-4 tests are completed, try to identify

the mineral, then... Bring the mineral to Mrs. McMullan when

finished to see if you are correct and to get another mineral to identify.

Questions for review Which of the following definitions best describes

a MINERAL?– a. a substance that cannot be separated or

broken down into simpler substances by chemical reactions

– b. a substance made up of atoms of two or more different elements joined by chemical bonds

– c. a naturally formed inorganic solid that has a definite crystalline structure

– d. a solid whose atoms, ions, or molecules are arranged in a definite pattern

Minerals that contain one or more elements combined with silicon and oxygen are called _________ {enrich}

silicates Which mineral can be identified by tasting? halite (salt) What is the difference between a mineral and

a rock? Minerals are elements or compounds. Rocks are mixtures (or minerals).