Minerals & Rocks

Minerals & Rocks

Minerals

5 Characteristics:

Naturally occurring Inorganic

Found as a solid in nature

Formed from elements or compounds

Definite chemical make up and regular atomic structure

A. Minerals are classified according to their properties.

Physical

and

Physical Properties: 1) Color - Easiest to recognize

Not very reliable Example: quartz - comes in several different colors

Chemical

calcite and halite ? both can be transparent and/or same color

2) Streak - the color of a mineral's powder Test: Rub the mineral across a piece of unglazed ceramic tile

3) Luster - the way a mineral reflects light

Metallic - looks like shiny metal

Non-Metallic- Does not look like shiny metal - Can be dull, waxy, glassy, ect.

Minerals and Rocks 43

4) Hardness - a mineral's ability to scratch or be scratched

Test: Find a sharp edge on your mineral and try to scratch the glass plate

Moh's hardness scale - 10 common minerals placed in order of hardness - the higher numbers can scratch the lower

numbers

Moh's hardness scale: 1. Talc 2. Gypsum 3. Calcite 4. Flourite 5. Apatite 6. Feldspar 7. Quartz 8. Topaz 9. Corundum 10. Diamond

5.5 ? approximate hardness of a glass plate

5) Cleavage - The tendancy of a mineral to split along smooth, flat surfaces called planes

Test: Look at the mineral carefully and check for light reflecting off of flat surfaces

6) Fracture - When a mineral breaks into pieces with uneven surfaces

7) Specific Gravity - the ratio between the weight of a substance and the weight of the substance in an equal volume of water - like density

8) Special Properties - Unique properties some minerals have

Examples - Halite ? tastes salty Magnetite ? magnets are attracted to it Calcite ? double refraction Calcite ? bubbles with HCl (hydrochloric acid) ? acid test

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B. Minerals are grouped according to their

1. The elements

silicon

and

form tetrahedral units.

Chemical properties

oxygen

combine to

Together, the mass of these two elements are most abundant in the Earth's crust.

Silicates - any mineral composed of silicon and oxygen

Tetrahedron

oxygen

2. The physical properties of minerals depend upon the Internal arrangement of atoms

silicon

Example:

Diamond

- Jewelry - Cutting hard

substances

100 % Carbon

Graphite

- Pencil lead - Lubricant

3. Of the thousands of known minerals, only a few are found almost

everywhere

4. If you know how to identify about a

dozen of the most common minerals

you will be able to identify minerals in most rocks you are likely to find.

5. Nearly all rocks are composed of one or more

minerals

6. Minerals are the

building blocks

of most rocks.

Some exceptions include:

coal

and

limestone

C. Rocks are classified on the basis of their origin. - How they were formed

(a) Igneous - Formed from melting and solidification of magma

(b) Sedimentary - Deposition, burial, compaction and cementation of sediments

(c) Metamorphic - Formed from any rock type due to extreme heat and pressure

Minerals and Rocks 45

Minerals

Naturally occurring

solid

Characteristics

Internal arrangement

of atoms

color

streak

hardness

Physical Properties

46 ESworkbooks?2008cdunbar

inorganic

Definite atomic structure

Elements or compounds

luster

Special Properties

cleavage

taste magnetic

acid test

double refraction

Fill in the missing information in the chart below by using the "Properties of Common Minerals" in the Earth Science Reference Tables page 16

Luster Nonmetallic Nonmetallic Nonmetallic Metallic Nonmetallic Either Nonmetallic Nonmetallic Metallic Nonmetallic Metallic Nonmetallic Metallic Nonmetallic

Hardness 6 2 4 2.5 1

1-6.5 2 4 6.5 7 1-2 3

5.5-6.5 6.5

Composition KAlSi3O8 S CaF2 PbS

Mg3Si4O10(OH)2 Fe2O3

CaSO4?2H2O CaF2 FeSO2

Fe3Al2Si3O12 C

CaCO3 Fe3O4 (Fe, Mg)2SiO4

Color white to pink yellow to amber colorless/variable metallic silver white to green

earthy Red white to pink

colorless brassy yellow

dark red silver to gray colorless/variable black to silver green to gray

Mineral Name Potassium Feldspar

Sulfur Fluorite Galena

Talc Hematite Gypsum Fluorite

Pyrite Garnet Graphite Calcite Magnetite Olivine

Which mineral has the following characteristics?

Mineral Characteristics Bubbles with acid when powdered Cleaves at 56? and 124? Food additive and melts ice Easily scratched by a fingernail Red-brown streak Feels greasy Used in glass, jewelry and electronics Polarizing prism and used in cement

Mineral Name Dolomite

Amphiboles Halite Gypsum

Hematite Talc /Graphite

Quartz Calcite

Minerals and Rocks 47

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