Minerals Chapter 2

2 Element: a substance that cannot be broken down into simpler substances. Atom: smallest particle that contains the characteristics of an element. *Periodic Table: A table in which the elements are organized by their properties. 2

3 Periodic Table of Elements Rows=Periods Columns=Groups 3

4 Parts of the atom 1) Nucleus – the center of an atom. It contains subatomic particles called protons and neutrons. 2) Proton - a subatomic particle that has a positive (+) charge. 3) Neutron – a subatomic particle that has no charge (it is neutral). 4) Electron – a subatomic particle that has a negative (-) charge. It is found in areas surrounding the nucleus. 4

5 What makes atoms different from each other? Lithium has 3 protons Carbon has 6 protons Sodium has 11 protons The number of protons in the nucleus. This number is also the atomic number. 5 6 C Carbon 12.0

A carbon atom has ________ protons (hint: atomic number). In an atom the number of protons equals the number of electrons. (This keeps the atom’s charge neutral) Number of Neutrons=Atomic mass-protons (Isotopes are atoms of elements with different numbers of neutrons 6 C Carbon 12.0

Why Atoms Bond  An ion is an atom that gains or loses electrons...this means the atom is no longer neutral!  When an atom’s outermost shell isn’t full, it is likely to form a chemical bond with one or more atoms. - A compound is made of 2 or more elements chemically joined

Types of Chemical Bonds 1. Ionic – form between positive & negative ions 2. Covalent – when atoms share electrons 3. Metallic – when metal ions share electrons

2.2 Minerals

Definition of a Mineral: 1. Naturally occurring 2. Solid substance 3. Orderly crystalline structure 4. Definite chemical composition 5. Generally considered inorganic

Mineral Groups 1. Silicates - Silicon & Oxygen join to form a structure called a silicon-oxygen tetrahedron, this provides the framework for every silicate mineral example: Quartz (most common)  Can be classified based on their composition

Mineral Groups 2. Carbonates - Contain carbon, oxygen, & 1 or more other metallic elements example: Calcite (most common)

Mineral Groups 3. Oxides - Contain oxygen & 1 or more other elements, usually metals example: Corundum (aluminum oxide)

Mineral Groups 4. Sulfides – contain sulfur example: Pyrite (fool’s gold)

5. Halides – contain halogen ion & 1 or more other elements example: Halite (table salt NaCl) Mineral Groups

6. Native elements – minerals that exist in relatively pure form example: Gold Mineral Groups

How Minerals Form 1. Crystallization from magma (as it cools) 2. Precipitation (what’s left behind when water evaporates) 3. Pressure/Temperature 4. Hydrothermal solutions

2.3 Properties of Minerals

Identifying Minerals: Color Most easily observed property Yet, least useful property

Identifying Minerals: Color Why it is the least useful property… Different minerals have the same color One mineral can have different colors Impurities can alter color Some change color when exposed to air Way a mineral shines in reflected light distorts color

Identifying Minerals: Streak Color of a mineral’s powder form Usually, streak is not the same color as the mineral Streak doesn’t vary

Metallic mineral=dark streak Nonmetallic= colorless or light streak Identifying Minerals: Streak Test

Identifying Minerals: Luster Way a mineral shines in reflected light

Identifying Minerals: Luster Metallic: shines like polished metal Pyrite “Fool’s Gold”

Identifying Minerals: Luster Nonmetallic: does not shine like metal

Identifying Minerals: Luster Pearly like a pearl Talc

Identifying Minerals: Luster Greasy Turquoise

Identifying Minerals: Luster Vitreous like shining glass Amethyst

Identifying Minerals: Luster Resinous like wax

Identifying Minerals: Luster Dull or Earthy Bauxite

Identifying Minerals: Crystal Shape The shape of a crystal results from the way the atoms of a mineral come together as the mineral forms

Identifying Minerals: Hardness Resistance to being scratched Moh’s hardness scale

Mohs Scale, identified numerically by standard minerals, from 1 (softest) to 10 (hardest): 1. Talc 2. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Orthoclase 7. Quartz 8. Topaz 9. Corundum 10. Diamond

T he G eologist C an F ind A n O rdinary Q uartz, (that) T ourists C all D iamond! To remember the Mohs scale try remembering this phrase:

Tools for Testing Hardness finger nail (H = 2.5) penny (H = 3.5) common nail (H = 4.5) glass plate (H = 5.5)

Identifying Minerals: Cleavage The splitting of a mineral along certain flat surfaces Related to the types of bonds in the internal structure of the mineral

Identifying Minerals: Cleavage

Identifying Minerals: Fracture the way a mineral tends to break Minerals that do not show cleavage when broken are said to have fracture

Identifying Minerals: Fracture jagged Splintery

Identifying Minerals: Special Properties Acid test

Identifying Minerals: Special Properties Magnetic test