matter and minerals

Matter and Minerals

Elements and the Periodic Table

Matter

Elements are the basic building blocks of minerals.

Over 100 elements are known.

Atoms Smallest particles of matter

Matter

Have all the characteristics of an element

• neutrons, which have neutral electrical charges

The nucleus is the central part of an atom and contains• protons, which have positive electrical charges

Atoms

Matter

Energy levels, or shells• surround the nucleus• contain electrons—negatively charged particles

The atomic number is the number of protons in the nucleus of an atom.

Model of an Atom

Isotopes

Many isotopes are radioactive and emit energy and particles.

Isotopes of an element have the same number of protons but varying numbers of neutrons.

Have different mass numbers: the sum of the neutrons plus protons

Matter

The mass number is the number of neutrons and protons in the nucleus of an atom.

Why Atoms Bond

• A compound consists of two or more elements that are chemically combined in specific proportions.

When an atom’s outermost energy level does not contain the maximum number of electrons, the atom is likely to form a chemical bond with one or more atoms.

Matter

• An ion is an atom that gains or losses electrons.

Types of Chemical Bonds 1. Ionic bonds form between positive and

negative ions.

Matter

2. Covalent bonds form when atoms share electrons.

3. Metallic bonds form when metal ions share electrons.

Minerals: the building blocks of rocks

• Definition of a Mineral: naturally occurring inorganic solid characteristic crystalline structure definite chemical composition

How do we identify minerals?

• Physical properties: Color Luster Hardness Crystal shape Cleavage Specific gravity Other

Physical Properties of Minerals

• Color:– Most obvious, but often misleading– Different colors may result from impurities

Example:Quartz


• Color: Streak – color of a mineral in powdered form

(used for metallic minerals)

Obtained by scratching a mineral on a piece of unglazed porcelain.

Example:Hematite

Streak• Red chalk on a chalk board

makes red marks. White chalk makes white marks.

• Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.

Gold• When gold is

run across a streak plate it makes a yellowish-gold color.

• That makes sense.

Pyrite or “Fool’s Gold”• When pyrite is run

across a streak plate, it has a black or dark green streak.

• Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.

Hematite• Hematite’s color is

grey, but its streak is red.

• Hema means blood.

• The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.

One mineral property we will

not use…COLOR

A mineral can be many different colors. Below is Mica.

Many minerals can be the same color. Below are gold colored minerals. Which one

is gold?

The answer…None of them

were real gold.

Just like with people…

Outside color does not tell you much about the

important characteristics.


• Luster:– How a mineral surface reflects light– Two major types:

• Metallic luster• Non-metallic luster

Metallicexample:Galena

Non-metallicexample:

Orthoclase

Pyrite (Fool’s Gold) Displays Metallic Luster.


• Hardness:– How easy it is to scratch a mineral– Mohs Scale of Hardness

• relative scale• consists of 10 minerals, ranked 1 (softest)

to 10 (hardest)

Mohs Scale of Hardness

Hardest (10) – Diamond

Softest (1) – Talc

Common objects:

- Fingernail (2.5) - Copper penny (3.5) - Wire nail (4.5) - Glass (5.5) - Streak plate (6.5)

Hardness• Is measured by how easy it is to

scratch. • Geologists order the hardness

by…1. Scratched by a fingernail.2. Scratched by a penny. 3. Scratched by a nail. 4. Scratched by a diamond.

These are not all of the tools geologists use, but it will work for

our experiment.

Gypsum is soft, it can be scratched by a fingernail.

Calcite is soft, but a little harder because it cannot be

scratched by a fingernail, but it can be scratched by a penny.

Fluorite is harder. It can be scratched by a nail, but not a

penny or fingernail.

Diamonds are the hardest mineral, so it scratches every

mineral.


• Crystal shape (or form):– external expression of a mineral’s internal

atomic structure– planar surfaces are called crystal faces– angles between crystal faces are constant for

any particular mineral

Quartz Pyrite


• Cleavage vs. Fracture:– The way a mineral breaks– Cleavage: tendency of a mineral to break

along planes of weakness

– Minerals that do not exhibit cleavage are said to fracture

Do not confuse cleavage planes with crystal faces! Crystal faces are just on the surface and may not repeat when the mineral is broken.


• Cleavage is described by:– Number of planes– Angles between adjacent planes

– These are constant for a particular mineral


• Cleavage (1 direction):

Example: mica

Mica Has Cleavage in One Direction


• Cleavage (2 directions):

orthoclase

amphibole



halite

calcite



fluorite


• Fracture:– minerals that do not exhibit cleavage are said to

fracture

– smooth, curved surfaces when minerals break in a glass-like manner: conchoidal fracture

Quartz

Conchoidal Fracture


• Specific gravity:– weight of a mineral divided by weight of an

equal volume of water– metallic minerals tend to have higher specific

gravity than non-metallic mineralsGalenaSG=7.5

QuartzSG=2.67

– reaction with hydrochloric acid (calcite fizzes)


• Other properties:

– taste (halite tastes salty)

– feel (talc feels soapy, graphite feels greasy)

– magnetism (magnetite attracts a magnet)

• Rock-forming minerals– ~30 common minerals make up most rocks in

Earth’s crust– Composed mainly of the 8 elements that

make up over 98% of the crust

Mineral Groups

Mineral Groups

All others: 1.5%

Element Abundances

Silica(SiO4)4-SILICATES

Common cations thatbond with silica anions

– Oxides O2-

– Carbonates (CO3)2-

– Sulfides S2-

– Sulfates (SO4)2-

– Halides Cl-, F-, Br-

– Native elements (single elements; e.g., Au)

Mineral Groups

• Silicates (most abundant)• Non-silicates (~8% of Earth’s crust)

Mineral Groups

FerromagnesianSilicates (Fe, Mg)

Non-ferromagnesianSilicates (K, Na, Ca, Al)

OxidesCarbonatesSulfides/sulfatesNative elements

Mineral Groups – Silicates

1. Silicates– Tetrahedron

• fundamental building block

• 4 oxygen ions surrounding a much smaller silicon ion

Silicon-oxygentetrahedron

(SiO4)4-


• Joining Silicate Structures– How tetrahedra may be linked:

• independent tetrahedra• single chains• double chains• sheets• 3-D framework

Mineral Groups– Silicates –

Olivine Groupdark silicates (Fe-Mg)


No cleavage

ferromagnesian

Pyroxene GroupFerromagnesian / dark silicates (Fe-Mg)


2-directionsof cleavage(at nearly 90 degrees)

Augite

Amphibole GroupFerromagnesian / dark silicates (Ca, Fe-Mg)


2-directionsof cleavage(not at 90 degrees)

Hornblende

Mica Group and Clay Mineralslight silicates (K, Al)


1-directionof cleavage

Muscovite

non-ferromagnesian

Feldspar Grouplight silicates (K-Na-Ca, Al)


2-directionsof cleavage

(at 90 degrees)

Orthoclase

Plagioclase

K-feldspar

Ca/Na-feldspar

Most common mineral group

Quartzlight silicates (pure SiO2)


no cleavage(conchoidal fracture)

hard, resistant to weathering Quartz

Mineral Groups

Minerals

2. Carbonates• Minerals that contain the elements carbon,

oxygen, and one or more other metallic elements

3. Oxides• Minerals that contain oxygen and one or more

other elements, which are usually metals

Mineral Groups

Minerals

4. Sulfates and Sulfides• Minerals that contain the element sulfur

5. Halides• Minerals that contain a halogen ion plus one or

more other elements

6. Native elements• Minerals that exist in relatively pure form

Sulfides

Native Copper

matter and minerals

Documents

streak color

number of protons

number of neutrons

gold colored minerals

yellowishgold color

goldwhen gold

metallic bonds form

mineral surface