Download chapter 3 Minerals notes

Chapter 3 minerals
Section 1
What is a mineral?
 Naturally occurring
 Inorganic solid
 Has a definite chemical composition
 Has an orderly arrangement of atoms
 About 4000 different minerals are found in earth
Mineral characteristics
 Formed by natural processes inside and outside earth
 Not made by life processes
 Every mineral is an element or compound
 Example – gold (Au) or salt (NaCl)
 Are crystalline solids with definite volume and shape
 Only a solid can be a mineral, but not all solids are minerals
Structure of minerals
 They are crystals with repeating patterns
 Crystal systems are groups of crystals that have similar external crystal shapes
 Not all crystals have smooth surfaces and regular shapes, like quartz
 Crystals form by many processes
Crystals from magma
 When magma cools slowly below ground, large crystals form, like in granite
 Magma that cools quickly has small crystals that are not able to be seen
Crystals from solution
 Crystals can form from minerals dissolved in water, like salt crystals left from
evaporated salt water
 Crystals also form without the need for evaporation when too much of a substance
is dissolved in water, like rock candy forming
Mineral composition and groups
 About 98% of the earth’s crust is made of only 8 of the 90 elements found on
earth
 Most rock forming minerals are silicates
 Silicates contain silicon, oxygen and at least one more element
 There is more silicon and oxygen in the earth’s crust than any other minerals
Section 2
Mineral identification
 Physical properties – individual minerals have unique properties that distinguish
them
 Mineral appearance – properties can help you recognize different minerals
Hardness
 Mohs scale is used to describe the hardness of a mineral.
 Scale runs from 1 to 10, with the softest mineral, talc, is 1 and the harness
mineral, diamond, is 10
 A harder mineral will scratch a softer one
Luster
 How a mineral reflects light
 Can be metallic (shiny) or nonmetallic (dull, pearly, glassy)
Specific gravity
 Can be seen by comparing two minerals heft
 The 2 minerals may look to be about the same size, but one will feel heavier
Streak
 When a mineral is rubbed against a surface that is harder than the mineral it will
leave a powdered streak
 Example – graphite on paper, chalk on slate
Cleavage and fracture
 Minerals will break along flat planes, like calcite, or they will break in a jagged
way, like quartz
Other properties
 Some minerals have special properties, like magnetism
Section 3
uses of minerals
 Gems are highly prized minerals because they are rare and beautiful
 They are brighter, clearer and more colorful than common samples of the mineral
useful gems
 Some gems, like diamonds, are used as abrasives and cutting tools
 Some gems are used to produce laser light
 Some are used in electronics – quartz
 Most gems used in industry are synthetic (made by humans)
Useful elements in minerals
 Ores – useful minerals that are mined at a profit
 Extracting elements – minerals need to refined or separated from other unwanted
materials using a heating process called smelting
Vein minerals
 Some minerals are dissolved in fluids. They seep into cracks in rocks and form
deposits in the gaps in and between rocks
Minerals containing titanium
 Titanium is strong, nontoxic and lightweight
 Titanium contains the minerals Rutile and Ilmenite
 Used in bicycle frames, cars parts, airplanes, eyeglass frames, etc.