MINERALSPATTERNS IN NATURE

CMUBill PalmerLecture 4

Central Methodist University

What are Minerals?

Natural Chemically Pure Make up “rocks” Solid Inorganic Often form

crystals Crystal structure

is organized arrangement of atoms

How Rocks and Minerals Different?

ROCKS ARE COMPOSED OF

MINERALS

MINERALS ARE CHEMICALLY

PURE

Big important hint: Learn the Minerals and the Rocks will be easy to learn!!

Your Very Life Depends on Minerals

General Facts about Minerals

Between 2 - 3,000 have been identified A few are “native elements” -- made of only one

element, such as sulfur, gold. copper, and graphite (carbon)

Most are compounds, especially the silicate group (Si, O)

Other important groups are oxides, carbonates, and sulfides

About a dozen are common in most rocks

Quartz Feldspar (group) Muscovite (white

mica) Biotite (black

mica) Calcite Pyroxene

Olivine Amphibole

(group) Magnetite,

limonite, and other iron oxides

Pyrite Galena Barite

Common Uses Include:

Aluminum--packaging, transport, building Beryllium--gemstones, fluorescent lights Copper--electric cables, wires, switches Feldspar--glass and ceramics Iron--buildings, automobiles, magnets Calcite--toothpaste, construction

Minerals are identified by their key characteristics

Hardness Crystal shape

(form) Luster Color Streak

Cleavage/fracture Density (specific

gravity) Special properties

--reaction to acid --fluorescence --salty taste --magnetismLearn how to test minerals

for these characteristics instead of trying to memorize

each mineral!!With 3,000 different minerals it

would be next to impossible to learn all the names!!

Mineral Hardness

Ability to scratch another mineral

Mohs scale from 1 (talc) to 10 (diamond)

Quartz (most common mineral and most dust particles) is 7

Mineral HardnessHARDNESS OF SOME COMMON ITEMS: MOH’S SCALE

2.5 Fingernail 2.5–3 Gold, Silver 3 Copper Penny 4-4.5 Platinum 4-5 Iron 5.5 Knife Blade 6-7 Glass 6.5 Iron Pyrite 7+ Hardened Steel

File

1 Talc Talcum powder. 2 Gypsum Plaster of Paris.

Gypsum is formed when seawater evaporates from the Earth’s surface.

3 Calcite Limestone and most shells contain calcite.

4 Fluorite Fluorine in fluorite prevents tooth decay.

5 Apatite When you are hungry you have a big "appetite".

6 Orthoclase Feldspar In German, "feld" means "field".

7 Quartz   Found everywhere. 8 Topaz The November

birthstone. Emerald and aquamarine are varieties of beryl with a hardness of 8.

9 Corundum Sapphire and ruby are varieties of corundum. Twice as hard as topaz.

10 Diamond Used in jewelry and cutting tools. Four times as hard as corundum.

Crystal Shape (Form)

External structure due to internal arrangement of the atoms

Six basic groups of shapes, with about three dozen variations

Luster Describes how

light reflects off the surface

Main categories are “metallic” and “non-metallic”

Non-metallic dull glassy waxy pearly

Color Results from ability to absorb some wavelengths and reflect others

Some minerals have characteristics colors

Others vary due to chemical differences or impurities (atoms mixed inside the main elements)

COLOR is usually the worst way to identify a mineral.

Streak Color of the powder

when rubbed on a “streak plate” (unglazed porcelain)

May be same as hand-specimen or different

Some paint is based on powdered minerals (streaks)

Mineral cleavage/fracture

Some minerals split along flat surfaces when struck hard--this is called mineral cleavage

Other minerals break unevenly along rough or curved surfaces--this is called fracture

A few minerals have both cleavage and fracture

Due to how the atoms are arrangedBe sure you understand the difference between

CLEAVAGE and FRACTURE.

Density (Specific Gravity) All minerals have density

(mass / volume), but some are very dense

Examples include galena, magnetite, and gold

Specific Gravity is the density of the mineral compared with density of water

Remember our Lab? Some minerals just feel

“heavy”

Special Characteristics--the “Acid Test”

Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)

Special Characteristics-- Fluorescence

Some minerals will glow when placed under short-wave or long-wave ultraviolet rays

Franklin and Ogdensburg NJ are famous for their fluorescent minerals

Special Characteristics--Salty Taste

DO NOT TASTE MOST MINERALS!

Halite is the exception--it will taste salty

Kaolinite (clay) will stick to your tongue

Special Characteristics--Magnetism

Many iron minerals will produce an invisible magnetic force field

“Lodestone” was used by Vikings more than 1,000 years ago as compassesMagnetite

A detailed look at some common minerals

OrSome common minerals that make-up most

rocks and some minerals your kids may ask you what they are and you will want to know so you

can impress them.

Quartz

Very hard 7.0 Many, Many forms

Clear Rosy=pink Milky=white Smoky=black Chalcedony=multicolor Agate=color rings Chert=white, brown, tan (very common) Mozarkite=pink/purple bands (MO State Rock) Amethyst=purple Jasper=dark blood red

QuartzWhich is which?

QuartzWhich is which?

Amethyst

Mozarkite

Agate

Rosy QuartzChert

Jasper

Smoky

MilkyChalcedony

Clear

Feldspar Hard 6.0 Vitreous, pearly Good Cleavage,

breaks at 900

Plagioclase Sodium Calcium Aluminum

silicate White, Yellow, Pink Striations

Orthoclase Potassium Aluminum

Silicate White, yellow, pink NO Striations

How to Identify Feldspars

pink dark

Check the Color

light

Check for

Striations

ORTHOCLASE FELDSPAR

PLAGIOCLASEFELDSPAR

yes no

Mica Soft 2.5-3.0 “Saran Wrap” Breaks in thin

layers Biotite

Dark

Muscovite Clear

Calcite Soft 3.0 Excellent

cleavage in 3 directions NOT 900

Colorless

White

Yellowish

Rhombohedrons

Pyroxene Hard 5.5-6.0 “Augite” Dark Green to

Gray Eight-sided

prisms

Olivine Hard 7.0 White Streak Pale to dark olive

Green Peridot is the

Gemstone

Amphibole Hard 5.5 White to gray

Streak Dark gray to

black

MagnetiteHematite, Limonite

Iron Oxides Iron Ores Color Varies with

amount of Iron Limonite = yellow Hematite =

reddish Magnetite =

black Tell apart by

streak

Pyrite Hard 6.0-6.5 Dark gray Streak Brassy yellow “Fool’s Gold”

Galena Soft 2.5 Silver Gray Metallic Perfect Cubes MO State Mineral Source of Lead

Barite Soft 3.0-3.5 White, but can

be stained reddish with iron

Heavy “Tiff” of S MO

Wrap-ups

1. Research the common uses for the 12 common minerals in the lecture.

2. List the diagnostic characteristics of minerals and include some of the possible variations.

3. What is the difference between a rock and a mineral?

4. Define a mineral. 5. What Moh’s Scale and what are some

hardness of some common objects.

Wrap-ups

6. What is a crystal? Do all minerals form crystals? What causes a crystal?

7. What is luster? What are the main types?

8. Distinguish between cleavage and fracture.

9. Why is color a poor distinguishing characteristic when identifying minerals?

10. What is the Missouri State Mineral?

Useful Web Sites

www.mii.org www.mineral.galleries.com/mine

rals www.mineral.net www.usgs.gov