MINERALS

ESSENTIAL QUESTIONS:

1. What are minerals made of?

2. How are minerals formed?

3. How does the elemental composition change the properties of minerals?

A NATURALLY OCCURRING,

INORGANIC SOLID WITH A DEFINITE

CHEMICAL COMPOSITION AND

CRYSTAL STRUCTURE.

DEFINITION

ATTACK!

What does it mean?

What is confusing?

MINERALS ARE…• Inorganic• The building blocks of rocks.• Found in the earth and are naturally occurring

substances. They are found in dirt, rocks, and water. They are not made by man.

• Usually solid crystals• About 2,000 minerals have been found.• Some minerals are rare and expensive. They

are called gems.

ATOM Smallest unit of an element.

ELEMENT An element is a substance that is made

entirely from one type of atom. It cannot be broken down into any

simpler substances by chemical methods.

COMPOUND A substance that results when the

atoms of two or more elements are chemically combined.

INORGANIC Not made of living organisms or the

remains of living organisms.

CRYSTALLIZATION This is a process in which crystals are

formed. It has to do with solvents and heating them and then cooling them - when they are cooled they will form crystals.

MINERAL FORMATION Almost all minerals form from

magma, the molten rock beneath the earth’s surface.

When magma cools, mineral crystals are formed.

WHEN MAGMA COOLS SLOWLY, LARGE CRYSTALS FORM.

WHEN MAGMA COOLS RAPIDLY, SMALL CRYSTALS FORM.

WHEN MAGMA COOLS VERY, VERY QUICKLY ON THE EARTH’S SURFACE, NO CRYSTALS WILL FORM.

MINERAL FORMATIONEvaporation Some minerals form

from solutions evaporating. Elements and compounds that had been dissolved now crystallize and are visible.

MINERAL FORMATIONTHE PRESSURE PROCESS When a rock is subjected to high

temperature and pressure, the minerals can begin to break down chemically.

The temperature and pressure becomes great enough to change the minerals in a solid state, without melting them.

The free atoms, ions, and molecules recombine in new ways, forming new minerals. More growth occurs in directions away from the pressure.

ATOMS, ELEMENTS, COMPOUNDS

Minerals have an orderly arrangement of atoms.

Minerals have a definite chemical composition – they

are each unique.

More than 90 % of the minerals in Earth’s crust are compounds containing oxygen and silicon, the two most abundant elements.

Most minerals are compounds; a few are composed of a single element.

ELEMENTS AND MINERAL PROPERTIES Minerals containing radioactive

elements are radioactive Minerals containing metals are

usually very dense Minerals containing silica (from

magma) are usually very light colored

Colors of minerals are determined by the elements they are made of

DIAMOND VS. COAL & GRAPHITE Coal, Graphite, and Diamond are all

made out of the element Carbon.

Why are they all different?

DIAMOND VS. COAL & GRAPHITE

Heat and pressure

change coal into a

diamond.

DIAMOND VS. COAL & GRAPHITE

It is the change in crystal structure that results in the color change. Graphite is composed of flat sheets of carbon. Diamond is a 7-carbon crystal, which is 3-dimentional.

DIAMOND VS. COAL & GRAPHITE

Color is a result of light absorption or light reflection.

Black means that all possible colors are being absorbed.

White means that all colors are reflected. In the case of diamond, it is clear because light passes through it.

MINERAL CATEGORIES Native elements – naturally

occurring elements; pure and uncombined. They form the rocks of the earth’s crust.

Silicates – compounds containing silicon and oxygen.

Nonsilicates – compounds without the silicon and oxygen combination.

ESSENTIAL QUESTION:

How can minerals be tested to determine certain physical properties needed for classification?

PHYSICAL PROPERTY Characteristic that is observable in a

substance without changing the chemical composition of the substance.

COLORSulfur- yellow

Pyrite- fool’s gold

Azurite- blue

Malachite- green

COLOR NOT reliable:

Different minerals can have the same color

Some minerals have different colors.

Minerals can change color over time through weathering.

STREAK

The powder left behind when a mineral is rubbed on an unglazed ceramic tile.

Why might it useful to use both black and white tiles?

TEXTURE You can feel the mineral, but often

times that is not always reliable since it may have been altered by weathering or manufacturing.

A better judge of texture is grain size: Fine-grained, medium-grained, coarse- grained.

DENSITY Ratio of the mass of a substance to its

volume, expressed as g/cm³.

DENSITY

Use a scale to find the mass of a mineral sample in grams.

Use the displacement method we practiced before to find the volume of the mineral. The volume of solids is reported as cc or cm3

LUSTER Light reflected from the surface of a

mineral.

EXAMPLES OF LUSTERVitreous

Resinous

Earthy

Metallic

Pearly

Dull

Fibrous

Adamantine

Waxy

WHAT IS THE LUSTER OF THIS MINERAL?

WHAT IS THE LUSTER OF THIS MINERAL?

WHAT IS THE LUSTER OF THIS MINERAL?

WHAT IS THE LUSTER OF THIS MINERAL?

HARDNESS Measure of the ability of a mineral to

resist scratching.

HARDNESS

The hardness of a mineral also depends on the arrangement of atoms, or molecules and the strength of the chemical bonds between them.

MOH’S SCALE OF HARDNESS Standard against which the hardness of a mineral is tested.

MOH’S SCALE OF HARDNESS1. Talc-easily scratched with fingernail2. Gypsum-scratched with fingernail3. Calcite-scratched with copper penny4. Fluorite-scratched with steel nail5. Apatite-easily scratched with steel nail6. Feldspar-scratches glass with force7. Quartz-scratches glass with moderate

force8. Topaz-scratches glass with minimal

force9. Corundum-scratches glass easily10. Diamond-cuts glass

CLEAVAGE Splitting of a mineral along smooth, flat

surfaces. Some minerals tend to split evenly

along certain flat surfaces.

CLEAVAGE One directional

Peels off in layers Example- biotite and muscovite.

CLEAVAGE Two directional

Flat and shiny plains Example: feldspar

CLEAVAGE 3 directional

Calcite and halite

4 directional (x,y,z, and diagonal)

fluorite

FRACTURE

The uneven splitting of a

mineral.

CRYSTAL STRUCTURES

Crystals of each mineral grow atom by atom to

form a particular crystal structure.

If space is not restricted, a mineral will exhibit a crystal

pattern with a definite number of sides and specific angles.

CRYSTAL SYSTEMS

Geologists classify these structures into groups based on

the number and angle of the crystal faces.

CUBIC CRYSTAL STRUCTURE (AKA –

ISOMETRIC)All sides are equal

length and 90° apart.

TETRAGONAL CRYSTAL STRUCTURE

Two equal, horizontal, mutually perpendicular axes

Vertical axis is perpendicular to the horizontal axes and is of a different

length.

HEXAGONAL CRYSTAL STRUCTURE

Three horizontal axes meeting at angles of 120o and one perpendicular axis.

ORTHORHOMBIC CRYSTAL STRUCTURE

Results from the stretching of a

cubic crystal into a rectangle.

MONOCLINIC CRYSTAL STRUCTURE

TRICLINIC CRYSTAL STRUCTURE

Crystal Cave of Giants, Mexico

CRYSTAL SHAPES ACTIVITY:

Use the internet to research mineral examples of each of the 6 crystal structures. Each group must construct all 6 crystal shapes using the paper patterns. **please write your block and group number, the names of your examples and the crystal name on the pattern before you glue it!!!! In the classroom, hunt through the mineral samples to find a physical example of each crystal shape. Show Mrs. Weneck your findings. Place your crystal models in the closet on your block’s shelf.

MAGNETISM

Is the mineral magnetic?

ACID TEST

Does acid make the

mineral fizz?