What is a Mineralpages 103-114

the building blocks of rocks

Minerals of Earth’s Crust

Mineral definition

A mineral is a natural, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical properties.

Five characteristics

naturally formed inorganic crystalline structure solid definite chemical composition

Naturally Formed

Not man made, naturally occurring

 Inorganic

Organic means living so, this means non-living

Crystalline structure

The atoms are arranged in a pattern that repeats over and over

Solid

Definite volume and shape

Not a liquid or gas

Definite Chemical Composition

Its chemical composition may be written down in a formula and is fairly consistent or within a range Example:

Halite (salt) NaCl Galena (lead) Pb

Kinds of Minerals

More than 4,000 have been identified Fewer than 20 are common

These are called rock-forming minerals

These ten make up 90% of the crust

Quartz Orthoclase Plagioclase Muscovite Biotite Calcite Dolomite Halite Gypsum Ferromagnesian minerals

Ferromagnesian mineral

Contain iron and magnesium

Two groups of minerals

Based on chemical composition

Silicates Non-silicates--

Silicates—contain a combination of

Silicon, Si Oxygen, O Silicates make up more than 90%

of the Earth’s crust

Six Kinds of Silicate Mineral Arrangements Isolated-do not link with other silicon or oxygen

atoms Ring silicates—form rings by sharing oxygen atoms Single-chain silicates—form by sharing oxygen

atoms Double chain silicates—form when two single

chains of tetrahedra bond to each other Sheet silicates—form when each tetrahedron shares

three of its oxygen with other tetrahedra Framework silicates—form when each tetrahedron

is bonded to four other tetrahedra

Nonsilicates

5 groups Carbonates Halides Native elements Oxides Sulfates Sulfides

From page 105

Write name of group Composition do not

fail to write it all! An example of a

mineral form each group

Silica tetrahedra Lab Part 1

Materials Toothpicks Marshmallows

Page 106

Silicon tetrahedra lab part 2

Cut out the tetrahedron Arrange tetrahedron to form the six kinds

of silicate mineral arrangements (page 107)

Glue onto construction paper and label structures

Mineral Identification

Minerals are identified using their physical properties.

These include crystal form, hardness, cleavage, luster, color, streak, and specific gravity. 

Crystal Form

Crystal form is caused by the orderly internal arrangement of atoms

Quartz is the most commonly identified by its crystal form

Two or more minerals that have the same chemical composition but different

crystal structures are called

polymorphs.

Hardness

Moh's Scale of Hardness 10 Diamond9 Corundum8 Topaz7 Quartz6 Feldspar5 Apatite4 Fluorite3 Calcite2 Gypsum1 Talc 

Hardness of some common objects

2.5 Fingernail3 Penny5 Pocket Knife5.5 Window Glass7 Steel File 

Cleavage

The tendency of a mineral to break along planes of weakness.

Some have good cleavage, some poor.

It depends on the crystal structure and chemical bonds: the stronger the bond the poorer the cleavage.

Fracture 

A break that is not along a cleavage plane

Common type is conchoidal fracture.

Ex. QuartzBroken glass appearance

Or can be splinters and fibers--asbestos

Luster

The way light reflects from the surfaceI. MetallicII. Nonmetallic

a. Greasy

b. Silky

c. Pearly

d. Glassy

Color

Color is good for a few minerals like copper and turquoise, but is not a very reliable means of identification.

The majority of minerals appear in a variety of colors. Impurities can change the color.

Streak

The color of the powdered mineralMuch more reliable.

Drag the mineral across a streak plate.

Hematite--reddish brown to black, but usually reddish brown

Limonite--yellowish brown  

Specific Gravity

A mineral’s density

d=m/vDensity = mass/volume

Densities are compared to an equal volume of water

There is no unit

Quartz -- 2.65 Silver -- 10.5Gold -- 19.3

Other Tests

TasteHalite--NaCl has a salty taste 

Fizz

If a mineral contains CO3 it will effervesce (fizz) when you drop dilute HCl (hydrochloric acid) on it.

Ex. Calcite CaCO3 

Feel

Talc has a soapy feel 

Smell

Sulfur has a rotten egg smell

Kaolinite has an earthy smell 

Etc

Writes on paper--graphite Rusty look—limonite

How to Identify Minerals

This film reviews some of the tests covered in your notes.

Mineral Lab Test each of the minerals to

determine their physical properties, and then identify them using the chart.

Fill this in well. This is a major grade.