geology chapter 3: matter and minerals

Importance of Minerals-

have been used for thousands of years and have become even more important in our everyday lives since.

building blocks of rocks

Mineral-

is any naturally occurring inorganic solid that possesses an orderly crystalline structure and a definite chemical composition that allows for some variation.

Defining a Mineral

1. Naturally Occuring-

ormed by natural geologic processes, not produced in a laboratory.

Defining a Mineral

2. Generally Inorganic-

Many marine animals secrete inorganic compounds, such as calcium carbonate (calcite) to form their shells and coral reefs. If these materials are buried and become part of the rock record

geologists consider them minerals.

Defining a Mineral

3.Solid Substance-

Only solid crystalline substances are considered minerals. Ice (frozen water) fits this criterion and is considered a mineral, whereas liquid water and water vapor do not.

Defining a Mineral

4.. Orderly Crystalline Structure-

minerals are made up of atoms (or ions) that are arranged in an orderly, repetitive manner.

Defining a Mineral

5.Definite Chemical Composition that allows for some Variation-

For example the common mineral quartz has the formula SiO₂ which indicates that quartz consist of silicon and oxygen atoms in a 1:2 ratio

Defining a Mineral

4.. Orderly Crystalline Structure-

a. Some naturally occurring solids such as volcanic glass (obsidian)  lack

a.repetitive atomic structure and are not considered minerals.

Defining a Mineral

5.Definite Chemical Composition that allows for some Variation-

a. Although quartz comes in a

variety of variations, like purple (amethyst), pink (rose quartz), and orange (citrine).

In contrast to minerals, rocks are

more loosely defined.

Simply, a rock is

any solid mass or mineral like matter that occurs naturally on our planet

Most rocks, like granite occur as

aggregates of several different minerals.

The term aggregate implies that

the minerals are joined in such a way that their individual properties are retained.

what is a rock

hornblende

black grains

what is a rock

phaneritic texture

crystals are large enough to see without magnification

what is a rock

feldspar

white or pink, Opaque Rectangular prism-shaped

what is a rock

quartz

Usually in rounded glassy grains

what is a rock

Mica

(Biotite/muscovite) dark/golden sprakling grians

Four States of Matter:

plasma

●Liquids

●Gases

●Solids

Plasma-

composed of ionized gases as in the sun and stars

Matter- What is it?

Anything that has mass and occupies space

Matter- What is it?

Anything that has mass and occupies space is matter. This includes

water, all organisms, and the atmosphere, as well as rocks and minerals.

Matter- What is it?

Our main concern are solids because as stated in the definition,minerals are

solid substances

Atoms-

the smallest particles that cannot be chemically split. They do contain even smaller particles: protons, and neutrons electrons.

protons, and neutrons located in

a central nucleus that is surrounded by electrons.

protons, and neutrons located in a central nucleus that is surrounded by

electrons

Protons and neutrons are very dense particles with almost

identical masses,

Protons and neutrons are very dense particles with almost by contrast electrons have a

negligible mass about 1/2000 of a proton.

Both protons and electrons share a fundamental property called an

electrical charge

Protons (charge

 +1

Electrons

(charge -1)

Neutrons are

neutral with (charge 0)

Atoms: Building Blocks of Minerals

Each ring/shell can hold a specific number of electrons associated with an energy level.

The outermost shell generally contains the

valence electrons

valence electrons, can be transferred or shared with other atoms to form

chemical bonds

Elements are Defined by their Number of

Protons

Elements are Defined by their Number of Protons

The number of protons in the nucleus of an atom is called

the atomic number

The periodic table organizes elements so that those with similar properties line up in

columns, known as groups.

Why Atoms Bond

Ions

atoms or groups of atoms with unequal numbers of protons and electrons, thus having a non-zero charge.

Why Atoms Bond

Ions

Positive and negative ions are attracted to one another and may

●stick or chemically bond together.

Why Atoms Bond

Bonding

controlled by outermost shell (valence) electrons.

Why Atoms Bond

Bonding

Elements will typically be reactive unless

●their valence shell is full.

Why Atoms Bond

Ionic Bonds-

●Valence Electrons Transferred

Why Atoms Bond

Covalent Bonds-

●Valence Electron Sharing

Why Atoms Bond

Metallic Bonds-

Electrons ree to Move; results in high electrical conductivity

Properties of Minerals

Diagnostic properties-

 are useful in identifying an unknown mineral.

Properties of Minerals

Diagnostic properties-

EX:

The mineral halite has a salty taste, because so few minerals share this property, the salty taste is considered a diagnostic property.

Properties of Minerals

Ambiguous properties-

 are properties of certain minerals varying among different specimen of the same mineral.

Properties of Minerals

7 PHYSICAL PROPERTIES OF MINERAL S

1. COLOR

2. streak

3. luster

4. cleavage and fracture

5. hardness

6. crystal shape

7. density

Properties of Minerals

7 PHYSICAL PROPERTIES OF MINERAL S

streak

the color of the mineral in powder form

Properties of Minerals

7 PHYSICAL PROPERTIES OF MINERAL S
cleavage and fracture

how the mineral splits along weak areas

Properties of Minerals

7 PHYSICAL PROPERTIES OF MINERAL S

hardness

the ability to resist scratching (measured using Moh’s Hardness Scale)

Properties of Minerals

7 PHYSICAL PROPERTIES OF MINERAL S

density

how closely its molecules are packed together

Optical Properties

Luster-

The appearance or quality of light reflected from the surface of a mineral

Minerals that have an appearance of of metal, regardless of color, are said to have

metallic luster

Minerals with a dull coating or tarnish exhibit a

submetallic luster

●Most minerals have a nonmetallic luster

○Vitreous/glassy

○Earthy/dull - soil like

○Pearly

○Silky/greasy

Optical Properties

Color-

Although color is the most conspicuous characteristic of any mineral, it is considered a diagnostic property of only a few minerals

Optical Properties

Quartz. can come in a variety of colors but each has the same baseline formula

SiO₂

Optical Properties

Streak-

The color of the mineral in powdered form

Optical Properties

Ability to transmit light–

opaque,translucent, transparent

Optical Properties

Ability to transmit light–

no light transmitted

opaque

Optical Properties

Ability to transmit light–

Light but no image transmitted

translucent

Optical Properties

Ability to transmit light–

Both light and an image are visible

transparent

Mineralogists use the term crystal________to refer to the common or characteristic shape of individual crystals or aggregates of crystals.

form/shape/habit

Some minerals tend to grow equally in _____________●Whereas some tend to be elongated in one direction ●Or flattened if growth in one dimension is surpassed

●all three dimensions

Crystal Form

Example

Some minerals have the same crystal forms, (pyrite, galena, and halite) all occur as cubic crystals but they can be identified by additional optical properties.

Mineral Strength

Hardness-

a measure of the resistance of a mineral to abrasion or scratching

Mineral Strength

Hardness is determined by

rubbing a mineral of an unknown hardness against one of a known hardness to obtain a numerical value using the Mohs Hardness Scale.

Mohs Hardness Scale- consists of minerals arranged from

1 (softest) to 10 (hardest)

Cleavage-

 the tendency of a mineral to break (cleave) along planes of weak bonding.

Cleavage-

Not all minerals possess cleavage, but some

that do break along smooth planes of weakness constructed by the strength of their chemical bonds.

Cleavage Cont.

Cleavage is an important diagnostic property of minerals and recognizing it is essential in

identifying minerals.

Cleavage Cont.

Example

The minerals Augite and Hornblende look very similar, both being dark green to black in color, have equal hardnesses, and both having two direction of cleavage. BUT their cleavage differs because the planes of Augite intersects at about 90 degrees while Hornblende intersects at angles of 56 degrees and 124

Fracture

When minerals do not break along planes of cleavage, they fracture.

Fracture

Irregular fracture-

●produce uneven surfaces

Fracture

Conchoidal fracture-

●break into smooth curved surfaces resembling broken glass

Fractures

Irregular fracture-

Conchoidal fracture-

●Splintery/Fibrous fracture

Tenacity-

describes a mineral’s resistance to breaking, bending, cutting, or other forms of deformation

Tenacity

Most minerals are

●brittle and will fracture or exhibit cleavage when struck.

Tenacity

●Most minerals are brittle and will fracture or exhibit cleavage when struck.

By contrast, metals like copper and gold are malleable and can

be hammered without breaking

Tenacity

Other minerals are sectile and can be cut into

● thin shavings

Tenacity

Some are elastic and can bend and return to their

original shape after the stress is released.

most malleable metal

gold

Density and Specific Gravity

Density-

mass per unit volume

Density and Specific Gravity

Specific gravity

density relative to that of water.

Other Special Properties

Striations

straight parallel lines on the flat surfaces of crystal faces.

Other Special Properties

Magnetism

attracted to magnet.

Other Special Properties

Double Refraction

two images are visible when looking through the mineral

Other Special Properties

Chemical Tests

calcite effervesces (bubbles) in dilute HCl.

Mineral Groups

There are over ____known minerals and new ones are identified every year

4,000

Mineral Groups

Fortunately no more than a few dozen are abundant and make up most of the rocks of Earth’s crust, these are known as

rock forming minerals.

Mineral Groups

Only 8 elements make up the vast majority of these minerals, representing more than

98%

Mineral Groups

These elements are (in order of most abundant to least abundant):

●Oxygen (O)

●Silicon (Si)

●Aluminum (Al)

●Iron (Fe)

●Calcium (Ca)

●Sodium (Na)

●Potassium (K)

●Magnesium (Mg)

     Rock-Forming Minerals

Rocks are aggregates of minerals meaning that they are made up of minerals that retain their

individual properties.

 Silicate Minerals

Silicates-

Made up of the two most common elements in Earth’s crust, Oxygen and Silicon, combine to form the basic “building block” for the most common mineral group.

Silicate Minerals

The Silicate- Oxygen Tetrahedron

All silicates have the same fundamental building block, consisting of four oxygen ions that are covalently bonded to a comparatively smaller silicon ion, forming a tetrahedron- a pyramidal shape with four identical faces

Silicate Minerals

The Silicate- Oxygen Tetrahedron

tetrahedron-

a pyramidal shape with four identical faces

Silicate Structures
In some minerals, the tetrahedra joined form some of these basic structures for silicate minerals:

●Isolated Silicate

●Chain Silicates

○Single

○Double

●Sheet Silicates

●3D Framework Silicates.

Non-Silicate Minerals

Carbonates

●contains C O₃ in their structures (calcite – C a C O₃).

calcite: the most common carbonate material

Non-Silicate Minerals

Halides

●contains Cl, F, Br in their structures (halite - NaCl)