Chapter 5 Atoms, Elements, and Minerals

The next few chapters in geology are mostly about rocks The next few chapters in geology are mostly about rocks. Nearly all rocks are made of minerals, so in order to learn about rocks you need to know something about minerals. In Chapter 5, you will discover that: Each mineral is made up of specific chemical elements, the atoms of which are organized in a special arrangement. The chemical makeup and its internal structure determine an element’s physical properties. 3. A mineral can be identified by its physical characteristics, such as: cleavage, crystal form, fracture, hardness, lustre, colour, streak, and specific gravity.

What is Matter? Matter – the substance of which any physical object is composed. Everything is made of matter. States of Matter: Solid Liquid Gas Controlling factors: Temperature Pressure Examples: Gold Mercury Oxygen solid liquid gas

The stuff that makes up all matter The make-up of solid matter on Earth: Atoms  Elements  Compounds  Minerals  Rocks (smallest) (largest) What is an atom? An atom is the smallest particle of a matter that keeps the properties of that matter. For example, all sodium atoms are essentially identical to all other sodium atoms. Water (H2O) can be broken down into two atoms of hydrogen (H) and one atom of oxygen (O).

What are elements? Elements are the fundamental building blocks of matter. Elements cannot be broken down into smaller units. Elements are pure substances and are made of one or more of the same type of atoms. All elements are listed in the periodic table of the elements.

Periodic Table of Elements

Element abundances in the crust All others: 1.5%

What are the most abundant elements in the Earth’s crust? Oxygen (O) -Oxygen is the most abundant element in the crust (makes up about 50% of the crust) -Oxygen bonds easily with other elements

Silicon (Si) -Most silicon form bonds with oxygen to form silica -Quartz (SiO2) is pure silica that has been crystalized -Any mineral that contains silica is called a silicate

Aluminum (Al) -Aluminum is more common that iron, but difficult to separate from rocks because it binds very tightly with oxygen. Other elements in the Top 8 include: Iron Potassium Calcium Magnesium Sodium

Mineral characteristics Definition of a Mineral: naturally occurring inorganic solid characteristic crystalline structure definite chemical composition QUIZ!!! steel plastic sugar table salt mercury ice coal no, #1 no, #1 no, #1,2 YES! no, #3 YES! no, #2 basalt obsidian mica gold paper chalk coral no, #5 no, #4 YES! YES! no, #1,2 no, #2 no, #2

Mineral characteristics Naturally formed No substance created artificially is a mineral. examples: plastic, steel, sugar, paper Inorganic Anything formed by a living organism and containing organic materials is not a mineral. examples: wood, plants, shells, coal Solid Liquids and gases are not minerals. examples: water, petroleum, lava, oxygen

Mineral characteristics Characteristic crystalline structure must have an ordered arrangement of atoms displays repetitive geometric patterns in 3-D glass not a mineral (no internal crystalline structure) Definite chemical composition must have consistent chemical formula examples: gold (Au), quartz (SiO2), orthoclase (KAlSi3O8) basalt (like many other rocks) contains variable ratios of different minerals; thus, has no consistent formula

How many minerals are there? Nearly 4,000 types of minerals Only ~30 occur commonly (whew!) Why not more? Some combinations are chemically impossible Relative abundances of elements don’t allow more

Silicates Most minerals are silicates (which means they contain silicon & oxygen) Silicates have a very special structure called a tetrahedron. This tetrahedron is the building block of a the silicate crystals

Silicate tetrahedrons can combine together to make much bigger structures. Diamond is NOT a silicate, but pure crystallized carbon. It is a very strong tetrahedron (and also a mineral).

Minerals of the Earth’s Crust The following are silicate minerals. They are the most common minerals and make up about 90% of the crust. Feldspars Quartz Pyroxenes Amphiboles Micas

Feldspar Quartz Pyroxene Amphibole Mica

Other common mineral crystals include: 1. Clay minerals (which is another group of silicates) 2. Non-silicates Example: gypsum Example: calcite

Less common minerals of commercial value: Halite (salt) Diamond Gold Hematite & magnetite (iron) Chalcopyrite (copper)

Physical Properties of Minerals Colour Streak Lustre Hardness External crystal Cleavage (most important) Fracture Specific gravity

Class Activity 1.Briefly explain each of the physical properties of minerals. Refer to Properties of Minerals 2. ID some minerals (Resource) Video

Quiz Most common element in the crust. Most common mineral. Which one (or ones) is/are a mineral? Plastic quartz salt What is geology? What is the topic of your geology project?