Minerals

The Stuff that Rocks are made of

PowerPoint Notes created by S. KoziolDate : 9/1/2013 Revised : ?/?/??

Objectives What is a mineral?

Define a mineral.

Describe how minerals form.

Identify the most common elements in Earth’s crust.

LiroconitePotash

Sphalerite Gold

MineralsMinerals always exist in a solid(1) form.

Salt

Minerals (continued)

A naturally occurring(2) substance is one that is made by natural processes. Thus, a substance developed in a lab, such as a synthetic diamond, cannot be considered a mineral. An inorganic substance is one that is not alive nor has ever been alive. Therefore coal, formed by an organic process, is not a mineral.

Minerals - composition

Although a few minerals are composed of single elements, most are made from compounds.

Quartz

SiO2Olivine

(Mg,Fe)2SiO4

Solids with a specific chemical composition.(3)

Mineral - crystals

Crystal – Solid in which the atoms are arranged in repeating patterns(4)

Mineral – crystals (continued)A mineral can take the shape of one of the six major

crystal systems.

Magma

Magma - Molten material found beneath Earth’s crust.

Minerals - formation

Minerals can form when differences in density force magma upward into cooler layers of Earth’s interior.

Minerals - magmaWhen compounds in cooling magma no longer

move freely, they may interact chemically to form minerals.

Minerals – formation (continued)

Mineral crystals may begin to precipitate out of a solution that has become saturated.

Always have a scale in science

images

Minerals – formation (continued)

Minerals form from cooled magma and from elements in solutions.

Earth’s Crust – abundant elementsThe most abundant elements in Earth’s crust are

silicon and oxygen.

SilicatesSilicate - Mineral that contains silicon and oxygen. These make up the

most common mineral group.

SilicatesSub-classification based on tetrahedral structure

Non-SilicatesNatives elements – only one element Sulfides - with a sulfur; tellurium, arsenic, or selenium Oxides – O2

2-

Halides - (fluorine, chlorine, iodine, and bromine) is the main anion.Carbonates – [CO3]2-

Sulfates – [SO4]2-

Phosphates – [PO4]3-

http://ruby.colorado.edu/~smyth/min/minerals.html

Common Minerals

The most common minerals, feldspar and quartz, are silicates.

Think about it

If you took random samples of minerals from several locations, which type of mineral would you likely have more of—oxides, silicates, or carbonates. Why?

There likely would be more silicates than other types because 96 percent of the minerals in Earth’s crust are silicates.

Known MineralsThere are at least 4,900 known minerals in

Earth’s crust.

Ore

Minerals that contains a useful substance that can be mined for profit.

Peacock Ore - copperArgentite - silver

Ore - continuedThe classification of a mineral as an ore may

change once it has been mined.

Ore - continuedOres near Earth’s surface generally are obtained

from open-pit mines.“525 m deep, 1200 meters in diameter. The air zone within this mine is closed for helicopters - a few accidents occurred when they were “sucked in” by downward air flow…”

Gem

Valuable mineral prized for its rarity and beauty

Quiz Break

Remember there was a reason for taking those class notes . . .

Quiz Break

Objectives Of Identifying minerals

Classify minerals according to their physical and chemical properties.

Identify different types of minerals.

Discuss how minerals are used.

LiroconitePotash

Sphalerite Gold

ID-ing MineralsMinerals can be identified based on their physical

and chemical properties.

Physical Chemical

ID-ing Minerals - luster

Silver, gold, and copper have shiny surfaces and thus are said to have metallic luster.

Luster is described as either metallic or nonmetallic.

Gold Silver Copper

ID-ing Minerals - streak

A mineral’s streak rarely changes, but sometimes does not match its external color, even if it is weathered or its external color varies slightly.

ID-ing Minerals – trace elements

Trace elements in a mineral can affect the color or the value of mineral.

ID-ing Minerals – luster & streak

Luster is the way a mineral reflects light from its surface, while streak is the color of a mineral when it is broken up and powdered. Both are tests used to identify a mineral.

ID-ing Minerals – specific gravity

Geologists commonly use specific gravity as a measure of density for accurate identification of a mineral.

ID-ing Minerals – density vs. specific gravity

Density is the ratio of the mass of a substance divided by its volume. Specific gravity is the most common measure of density. It is the ratio of the weight of a substance to the weight of an equal volume of water.

ID-ing Minerals - hardness

Mohs scale is used to compare the hardness of minerals.

Finger nail ~2.2

Glass, steel knife ~ 5.5

Streak plate 7

ID-ing Minerals - cleavage

Mica has perfect cleavage in one direction; it breaks in sheets.

ID-ing Minerals - fracture

When flint and opals break, they have a unique fracture with arclike patterns.

ID-ing Minerals – cleavage & fracture

Minerals with cleavage split easily and evenly along one or more planes, while minerals with fracture break unevenly along jagged edges. Both describe how minerals split due to their atomic arrangements.

ID-ing Minerals – hardness & texture

Hardness is a measure of how easily a mineral can be scratched, while texture describes how a mineral feels. Both are tests used to identify a mineral.

ID-ing Minerals - inorganicA mineral, such as salt, is naturally occurring but

inorganic, in contrast to sugar, which comes from plants.

The most reliable way to identify a mineral is by using a combination of several tests.

cleavage - Property of splitting along one or more flat planes evenly and easily

fracture - Property of breaking with rough or jagged edges

hardness - Measure of how easily a mineral can be scratched

streak - Color of a mineral when it is broken up and powdered

luster - The way a mineral reflects light from its surface

Why do geologists usually use a combination of tests to identify a mineral?

Some minerals have characteristics similar to other minerals. Therefore, more than one test may be necessary to accurately identify the minerals.

ID-ing Minerals – specific gravityMineral Specific Gravity Chemical Formula Breakage Pattern

Gold 19.3 Au HacklyApatite 5 Ca5(PO4)3(F, OH, Cl) Uneven fracture

Pyrite 5.2 FeS2 Uneven fracture

Garnet 3.5–4.3 (Mg, Fe, Ca) 3

(Al2Si3O12)

Conchoidal fracture

Beryl 2.75 Be3Al2Si6O18 Uneven fracture

Corundum 4 Al2O3 Fracture

If the volume of the sample of beryl equals the volume of the sample of gold, how many times greater is the mass of the gold sample than the mass of the beryl sample?

SG 19.3 ÷ 2.75 = 7.02 times greater

ID-ing Minerals - HardnessMineral Color HardnessGold Metallic gold 2.5–3Apatite Blue, green 5Pyrite Metallic pale brass, gold 6–6.5Garnet Red, deep red, brown 6.5–7.5Beryl Bluish green, green 7.5–8Corundum Red, deep red 9

ID-ing Minerals - HardnessMineral Color HardnessGold Metallic gold 2.5–3Apatite Blue, green 5Pyrite Metallic pale brass, gold 6–6.5Garnet Red, deep red, brown 6.5–7.5Beryl Bluish green, green 7.5–8Corundum Red, deep red 9

Which mineral can scratch at least one of the green stones? Which mineral can scratch neither green stone? Which mineral can scratch at least one of the red stones? Which mineral can scratch neither red stone? Which mineral can scratch only one of the green stones?

pyrite

gold

beryl

apatite

garnet

Quiz Break 2

Remember there was a reason for taking those class notes . . .

Quiz Break