Chapter 2: Rock-Forming Minerals

Jan. 11 - Jan. 16

Minerals are composed of eight (8) elements:

* Oxygen
* Silicon
* Aluminum
* Iron
* Calcium
* Sodium
* Potassium
* Magnesium

Proton

positive charge

Neutron

neutral charge

Electron

negative charge

Atomic Number

Number of protons in the nucleus and it determines the type of element

Atomic Weight

* the mass of protons and neutrons


* electrons have negligible mass

Ions

atoms or molecules that possess an electric charge from having lost or gained an electron

Cation

a positively charged ion (LOSS of electron)

Anion

a negatively charged ion (GAIN of electron)

Isotope

different atomic weights of same element

Radioactive Isotopes (Daughter Isotopes)

* nuclei that decay at a constant rate to form other isotopes


* By measuring the amount of decay, such isotopes have undergone while present in the rocks
* this is important to geologists because they help work out the age of a fossil

Non-Radioactive Isotopes (Stable Isotopes)

* like O^18 and O^16
* They shed light on aspects of Earth’s history
* This is important to geologists because they serve as a proxy for a biological process

Ionic Bonds

* transfer electrons between atoms
* one atom loses an electron, it becomes positively charged
* the atom that gains an electron becomes negatively charged
* opposite charges attract

Covalent Bonds

* share electrons between atoms

Metallic Bonds

* valence electrons move freely among atoms
* atoms give up their electrons that then move and interact with all other positively charged ions in the structure
* good conductors of electricity and heat
* ________ minerals include: copper, gold, silver, etc.
* this is why ______ are such good conductors for heat

Crystal Lattice

* 3-D molecular structure of a mineral
* Its configuration reflects relative sizes and numbers of ions that make up the mineral

To form a stable compound, what do ions must have?

* Ionic charges balanced
* The right size to allow them to fit together
* EX: halite

Cation Substitution

* cations of similar size and charges tend to be **substitute** for one another in the crystal lattice
* can form compounds having the same crystal structure, but different chemical composition

Colour

* the most obvious property of a mineral, but can be misleading


* different colours may result from impurities

Streak

* colour of a (metallic) mineral in powdered form
* obtained by scratching a mineral or unglazed porcelain tile
* the streak is a “trail” of crushed powder of the mineral being tested

Diaphaneity

* a mineral’s ability to transmit light

Luster

how a mineral surface reflects light

Hardness

how easy it is to scratch a mineral

Crystal Shape

external expression of a mineral’s internal atomic structure

Crystal Faces

* planar surfaces
* angles between _____ ___ are constant for any particular mineral

Cleavage

* the way a mineral breaks
* tendency of a mineral to break along planes of weakness
* varies inversely with bond strength (weak bonds produce good cleavage)
* ionic bonds produce good ________

Fracture

* minerals that do not exhibit cleavage
* smooth, curved surfaces when minerals break in a glass-like manner

Conchoidal Fracture

(ie. Quartz)

* smooth, curved surfaces when minerals break in a glass-like manner

Density

* mass per unit volume g/cm
* weight of a mineral divided by weight of an equal volume of water

Specific Gravity

* __ of 1 means a density equivalent to water
* metallic minerals tend to have higher _____ _____ than non-metallic minerals (Pb)

What happens to

(a) calcite and;

(b) gypsum

when it’s mixed with HCl acid?

(a) Calcite fizzes,

(b) Gypsum does not.

What happens to

(a) halite; and

(b) carnallite

when you taste it?

(a) It tastes salty and

(b) it stings your tongue

How does

(a) talc and

(b) graphite

feel when you touch it?

(a) It feels soapy and

(b) It feels greasy

Magnetite

* attracts a magnet

Luminescence

* emits light when radiated with UV light

Silicates

* abundance of the elements of Silicon and Oxygen
* found in the crust and mantle
* contain silicon bonded to oxygen (SiO4)-4 in a structure known as silica tetrahedron
* formed at high temperatures

Silica Tetrahedron

* silicates have this unit structure that contain ____ _________
* 4 Oxygen atoms (-8) surround a much smaller silicon atom (+4)
* can only be bonded at the corners with similar SiO4 units (covalent bonds) and/or positively charged element (ionic bonds)

What is the most common sulfate mineral and its properties?

Gypsum

* it does not react w/ HCl
* its hardness scale is 2, which can easily be scratched with fingernail

What is Gypsum’s chemical equation?

CaSO4 with 2H2O

What are two iron oxide minerals?

Magnetite and Hematite

How can you distinguish magnetite and hematite from each other?

Magnetite’s colour is black, while Hematite’s colour is rusty orange.

What are two halide minerals?

Halite (NaCl) and Sylvite (KCl)

What are the consolidated solid material comprised of aggregates of one or more minerals or solidified organic material?

Rocks

What are examples of carbonate minerals?

Calcite (CaCO3) and Dolomite (Ca, Mg)CO3

Carbonates

Carbonate anion group (CO3 2-) combines with +2 cations (Ca, Mg, Fe)

* Mostly chemical sedimentary, but also some metamorphic

What are examples of sulfate minerals?

Gypsum (CaSO4 x 2H2O) and Anhydrite (CaSO4)

Sulfates

Sulfate anion group (SO4 2-) combines with +2 cations (Ca, Br, Sr)

What are examples of sulfide minerals?

Lead (Pb) and Zinc (Zn)

Sulfides

Have the sulfide anion (S 2-)

What are examples of oxide minerals, especially iron oxides?

Magnetite (Fe3O4) and Hematite (Fe2O2)

Oxides

Have the Oxygen ion (O 2-)

What are examples of halide minerals?

Fluorite (CaF2) and Halite (NaCl)

Halides

Chloride (Cl -)

Fluoride (F-)

Bromide (Br-)

Iodide (I-)

What are examples of native element minerals?

Gold (Au) and Silver (Ag)