1. Chapter 13 Minerals of The Earth’s Crust

2. I. What is a Mineral?
-a naturally formed, inorganic solid that has a definite crystalline structure.

3. Mineral Structure To be a mineral, a substance must be a solid
be inorganic
have a repeating inner “crystalline” structure
be formed in nature

4. Atoms & Compounds
Minerals are made up of atoms of one or more elements. Elements are pure substances made of only one kind of atom. They cannot be broken down into simpler substances by ordinary means.
An atom is the smallest part of an element that has all the properties of that element.

5. Atoms & Compounds cont.
Compounds are substances made of 2 or more elements that have been chemically combined. Example: NaCl (salt) is a compound made of Na (sodium), a metal, and
Cl (chlorine), a gas. Most
minerals are made of compounds but some
are composed of just
one element and are
called native elements.

6. Crystals
Solid, geometric forms of minerals produced by a repeating pattern of atoms or molecules that is present throughout the mineral are called
crystals. Each crystal
has a definite shape
determined by the
arrangement of atoms or molecules within the
crystal, and each mineral has
a definite crystalline structure. Minerals can be
grouped into classes according to the crystals they form.

7. Silicate Minerals
Minerals are divided into 2 groups based on their chemical composition:
Silicate minerals-minerals that contain a combination of silicon and oxygen, Earth’s 2 most common elements that make up more than 90% of the Earth’s crust.
Examples: quartz, feldspar, and mica
quartz feldspar mica

8. Nonsilicate Minerals are minerals that do not contain a combination of the elements silicon and oxygen. Some are made up of elements such as carbon, oxygen, fluorine and sulfur. Examples: copper, calcite, fluorite, corundum, gypsum, galena and others.
galena
copper calcite fluorite corundum gypsum

9. II. Mineral Identification

10. Color
The same mineral can come in a variety of colors, depending on what impurities are present and exposure to air and water for long periods of time.
Color is not the best way to identify a mineral.

11. Luster -is the way a surface reflects light
-Example: is something shiny or dull
metallic-bright, reflective
submetallic-dull, metallic or nonmetallic
nonmetallic-
6 different
descriptions

12. Streak -Streak is the color of a mineral in powdered form It can be found by rubbing the mineral against a piece of unglazed porcelain called a “streak plate” The color of a mineral’s streak is not always the color of the mineral sample, and is not affected by air or water. Streak is more reliable for identification than color.

13. Cleavage and Fracture
The way a mineral breaks is determined by the arrangement of its atoms.
Cleavage is the tendency of some minerals to break along smooth flat surfaces.
Fracture is the tendency of some minerals to break unevenly along curved or
irregular surfaces.

14. Hardness
This is a mineral’s resistance to being scratched. Scientists use the
Mohs Hardness Scale shown below. Talc has a rating of 1 and diamond has a rating of 10. If the reference mineral scratches your mineral, then the reference mineral is harder than your mineral.
MOHS HARDNESS SCALE

15. Density Gold on chunk of pyrite-”fool’s gold”
This is the measure of the amount of matter in a given amount of space. It is a ratio of an object’s mass to it’s volume. Water has a density of 1 g/cm³ and so is used as a reference point for other substances. The ratio of an object’s density to the density of water is called its specific gravity.
Gold has a specific gravity of 19 and so contains 19 times as much matter as 1 cm³of water contains. Pyrite (fool’s gold) has a specific gravity of 5. Specific gravity can be used to distinguish between gold and “fool’s gold”.
specific gravity ~ how heavy something feels when compared to what you would expect, heft, weight, mass, density
Gold on chunk of
pyrite-”fool’s gold”

16. Special Properties
The following special properties help identify a few types of minerals:
Fluorescence-calcite and fluorite glow under UV light
Magnetism-magnetite and pyrrhotite are natural magnets that attract iron
Chemical reaction-calcite will become bubbly or “fizz” when a drop of weak acid is place on it
Taste-Halite has a salty taste
Optical Properties-Calcite will cause a double image when placed over an image.
Radioactivity-Minerals that contain radium or uranium can be detected by a geiger counter

17. III. The Formation, Mining and Use of Minerals

18. Minerals form in a variety of environments in the Earth’s crust with different physical and chemical conditions which determine the mineral properties.

19. Surface Mining
When mineral deposits are located at or near the surface of the Earth, surface-mining methods are used to remove the minerals.

20. Mineral deposits called ores are mined for profit through surface or subsurface mining.
The method miners choose depends on how close to the surface or how far down in the Earth the mineral is located.

21. Open-Pit Mining
is used to remove large, near-surface deposits of economically important minerals such as gold and copper.
is mined downward, layer by layer
explosives are used to break up the ore
ore is loaded into trucks and taken away for processing

22. Open-Pit Mining
Trucks the size of houses dump 200-ton loads of waste rock, remnants of mineral mining from an open pit mine in Nevada.

23. Quarries
Are open pits used to mine building stone, crushed rock, sand and gravel

24. Strip Mining
Surface mining of coal is done in strips that may be 50m wide and 1 km long

25. Subsurface Mining cont.

26. Subsurface Mining
This method is used when mineral deposits are too deep within the Earth to be surface mined.

27. Subsurface Mining continued
Subsurface mining often requires that passageways be dug into the Earth to reach ore. These passageways may be dug horizontally or at an angle.

28. Subsurface Mining continued…
Sinkholes can result!

29. Wall of coal-mining pit near
Haybro, Colorado

30. Responsible Mining
Mining can destroy or disturb the habitats of plants and animals. The waste products from a a mine may get into water sources, which pollutes surface water and groundwater.

31. Mine Reclamation
When land used for mining is returned to its original state or better, it is called reclamation.
During Mining
After Reclamation

32. The Use of Minerals 1 Common Uses of Minerals Mineral Uses Copper
electrical wire, plumbing, coins
Diamond
jewelry, cutting tools, drill bits
Galena
batteries, ammunition
Gibbsite
cans, foil, appliances, utensils
Gold
jewelry, computers, spacecraft, dentistry
Gypsum
wallboards, plaster, cement
Halite
nutrition, highway de-icer, water softener
Quartz
glass, computer chips
Silver
photography, electronics products, jewelry
Sphalerite
jet aircraft, spacecraft, paints

33. Uses of Minerals

34. Metallic Minerals have shiny surfaces
good conductors of heat and electricity
can be processed into metals that are strong and do not rust
other metals can be pounded or pressed into various shapes
metallic minerals that have many industrial uses are gold, silver, and copper.