Mineral Properties & Identification

The story of minerals so far….• Minerals formed from elements that originated in exploding

stars, made a nebula and then formed our solar system• Minerals are solid, naturally occurring, inorganic, made of

chemical elements and have an internal arrangement of atoms (crystal structure)

• Native minerals are made of 1 element: gold, sulfur, iron• Top elements that make up the Earth’s crust are: oxygen, silicon,

aluminum, iron, calcium, sodium, potassium, magnesium• Most minerals are compounds: NaCl, CaCO3 SiO2

• A rock is a mixture of 1 or more minerals: granite• Limestone is made of only one mineral – calcite.

Observe

• Minerals #1 - #39• Separate/Group the minerals by properties:

– How are they alike? – How are they different?– Regroup them again using another similar property.

Properties used to Identify Minerals

• Color• Odor• Shiny or dull (Luster)• Hardness (scratches)• Streak color (on streak plate)• Solubility in water• Dissolve in water or react in acid• Cleavage (split or shatter when hammered)

More properties to I.D. minerals

• Optical properties: double refraction• Magnetic• Heavy (specific gravity)• Crystal shape• Fluorescent• Taste?• Radioactive

In each Mineral I.D. Lab bag:

1 Hand lens 1 yellow

1 Penny 2 clear

1 Glass plate 2 pink

2 Streak plates 1 dark red

1 magnet 1 flat

1 Nail 1 gold

8 minerals

Physical Properties of Minerals

• Color: light or dark, yellow, gold, pink….

• Luster: – metallic, – Non-metallic: dull, glassy,

vitreous, pearly, adamantine

Light: transparent, opaque, double refraction,

Streak• The color of the mineral in its powdered form.• Rubbing the mineral on a streak plate.• Streak is more reliable than color: • Streak is a consistent property of a mineral.• Metallic minerals generally have a dark streak,

– Non-metallic mineral do not

Two different colored forms of the SAME mineral: SAME colored streak

Mohs scale of hardness

Hardness

• Relative scale: comparing the hardness of a mineral to a known object.

• 1-10 • Diamond being the

hardest 10• Talc is the softest 1

• Fracture

Quartz (glass) fractures and shatters

into irregular-shaped pieces with

no flat planes

• Cleavage: the tendency of a mineral to break along flat planes of weak bonding

Halite will cleave into many smaller pieces each with 3 planes at 90°

Three examples of perfect cleavage –3 flat planes (sides)

fluorite, halite, and calcite

MineralSpecimen Number

Color

Luster

Light

interaction

Streakcolor

Hardnessnumber

Cleavage

Or Fracture

Soluble in water

Solubility

in acid

Other Properties:Magnetism,

Fluorescence

Mineral namepage 700- 701

1

yellow

dull

opaque

yellow

1-2 fracture

insoluble

insoluble

Smells like rotten eggs

2

3

4

5

6

7

8

sulfur

Name ColorLuster

LightInteraction

Streak Hard-ness

Cleavage Smell Sol.water

Sol.acid

1YellowDull

Opaque Yellow 1-2 none RottenEgg!

IS IS

2 Gold, metallic,shiny

opaque black 6 none none IS SS?

3whitePearly, flat

Transparenttranslucent

none 2-3 Perfect!1 direction peels

none IS IS

4Clearshiny

TransparentDoublerefraction

Nonewhite

3 perfect none IS YES!FIZZ

5Clear, whiteShiny, Tastes salty

translucent none 2-2.5 Perfect!3 direction90° angle

none Yes!dis-solves

IS

6Dark red-browndull

opaque Red-brown

3-4 none None orearthy

IS SS

7Salmon pink opaque none 6 Good

2 direction

none IS IS

8Pink, clearglassy

translucent none 7 Nonefracturesconcoidal

none IS IS

sulfur

Pyrite

Mica(Muscovite)

calcite

Halite(Salt)

hematite

feldspar

Quartz

Determining the Specific Gravity of a Mineral

1. Get out a piece of notebook paper.

2. Title: SpG & Mineral I.D. (pg. 112-113)

3. Copy Data Table 1 on page 112.

5. Copy the formula on pg. 113

6. Collect the data using a balance

7. Use the table on pg. 113 to Identify the mineral

8. Answer questions #3-8 on page 113

Determining Specific GravityMineral Data Mass (g)

Mass in air

Mass suspended in water

Change in mass from air to water

Specific Gravity (calculated)

Specific Gravity (accepted value)

Name of mineral

SpG = Mass of mineral in air change in mass

Suspend the mineral from a piece of string in abeaker of water. Find its mass.

So, according to your data, which has a higher specific gravity? Metals or non-metals?

Specific Gravity of Some Common Minerals

SpG

Sulfur 2.1

Gypsum 2.3

Calcite 2.7

Chalcopyrite 4.2

Pyrite 5.0

Magnetite 5.2

Galena 7.2

PracticeCalculate the Specific Gravity of the mineral

using the mass measurements.

Mass in air: 15.0 g

Mass in water -12.0 g

SpG =

What mineral is this?

3 g

Mass in airLoss of mass

15.0 g 3.0 g

= 5.0

Mineral Flow Chartin your notebooks copy the chart below

• Color? dark or light _______________• Luster? Metallic or non-metallic ________• Streak? Black, brown or reddish________• Harder than glass? __________________• Cleavage? Yes, no cleavage, 1,2,3,4 planes • Mineral Name _____________