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Minerals
Dr. R. B. Schultz
The earth is made of rocks, which are in turn made of
minerals. In this part of the course we'll learn how
to identify common minerals and rocks.
In order for something to be classified as a mineral, it
must meet five (5) criterion:
Minerals are:
·
1. Naturally occurring,
·
2. Inorganic,
·
3. Have known chemical compositions
·
4. Have definite physical properties.
5. Are solid
·
They are usually (although not always) crystalline.
Common uses include:

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
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Aluminum--packaging, transport, building
Beryllium--gemstones, fluorescent lights
Copper--electric cables, wires, switches
Feldspar--glass and ceramics
Iron--buildings, automobiles, magnets
Calcite--toothpaste, construction
http://www.mii.org/commonminerals.php
** minerals can be elements or compounds **
Mineral Classification
Minerals are classified
based on
chemical composition
and
crystal structure.

Mineral Classification: Chemical Composition
Minerals are made of different ions bonded together.
Ions are charged atoms

Cations are positively charged whereas

Anions are negatively charged
Common ions in earth's crust:
O - most common ion (anion)
Si, Al, Fe, Ca, Na, K, Mg, (Cations)
Minerals are made mainly of these ions.
The number of each kind of atom in the molecule
determines the minerals properties
Mineral Classification: Crystal Structure
Crystal structure depends on sizes of
and charges on ions
Polymorphs -- same chemical composition,
different crystal structures
Calcite and argonite
http://www.outreach.canterbury.ac.nz/resources/geology/page2.shtml
Mineral Classification: Groups

Silicates: Most common mineral group
(contain silicon and oxygen)
Quartz, Feldspars, Ferromagnesian
 96% of Earth’s crust


Non silicates: do not contain silicates or
oxygen

Carbonates, halides, oxides, sulfates,
sulfides, native elements
Minerals are identified by their
key characteristics



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hardness
crystal shape
(form)
luster
color
streak



cleavage/fracture
density (specific
gravity)
special properties -reaction to acid -fluorescence
-salty taste
--magnetism
Mineral Hardness



Ability to scratch
another mineral
Mohs scale from 1
(talc) to 10
(diamond)
Quartz (most
common mineral
and most dust
particles) is 7
http://mineral.galleries.com/minerals/elements/diamond/diamond.htm
Hardness
Geologists rank minerals according to hardness using the Moh's scale
Moh's Hardness Scale
1.0
2.0
2.5
3.0
3.5
4.0
5.0
5.5
6.0
7.0
8.0
9.0
10.0
TALC
GYPSUM
FINGERNAIL
CALCITE
COPPER PENNY
FLUORITE (Note the spelling!)
APATITE
STEEL KNIFE BLADE/GLASS PLATE
ORTHOCLASE FELDSPAR
QUARTZ
TOPAZ
CORUNDUM (RUBY)
DIAMOND
Crystal Shape (Form)


External structure due
to internal
arrangement of the
atoms
Six basic groups of
shapes, with about
three dozen variations
http://www.minerals.net/mineral/carbonat/aragonit/aragoni1.htm
Luster

Describes how light
reflects off the surface

Main categories are
“metallic” and “nonmetallic”

Non-metallic includes
“dull,” glassy,” waxy,”
“pearly,” and others
http://www.minerals.net/mineral/sulfides/pyrite/pyrite2.htm
Non-metallic mineral
Metallic mineral
Color



results from ability to
absorb some
wavelengths and
reflect others
some minerals have
characteristics
colors
others vary due to
chemical differences
or impurities (atoms
mixed inside the
main elements)
http://www.minerals.net/mineral/carbonat/calcite/images/4assortd.htm
Streak
Color of the powder
when rubbed on a
“streak plate”
(unglazed porcelain)


Streak does not vary
even if color does

Some paint is based on
powdered minerals
(streaks).
http://www.minerals.net/mineral/oxides/hematite/hematit6.htm
Mineral cleavage/fracture

Some minerals split along flat surfaces when struck
hard--this is called mineral cleavage

correspond to zones of weak bonding in the
crystal structure.

Other minerals break unevenly along rough or
curved surfaces--this is called fracture

A few minerals have both cleavage and fracture
Cleavage
To describe cleavage, one must determine the number of
unique cleavage planes (directions) and their angle with
respect to each other
(e.g. salt breaks into cubes, with cleavage in 3 directions,
all at 90 degrees)
NO
cleavage
Density (Specific Gravity)

All minerals have
density (mass /
volume)

Specific Gravity is the
density of the mineral
compared with density
of water
http://www.minerals.net/mineral/elements/gold/gold1.htm
Special Characteristics–
the “Acid Test”
Carbonates react
with dilute HCl and
other acids by
fizzing or bubbling
(releasing CO2 gas)
Special Characteristics-Fluorescence


Some minerals will
glow when placed
under short-wave or
long-wave ultraviolet
rays
Franklin and
Ogdensburg NJ are
famous for their
fluorescent minerals
http://www.sterlinghill.org/Tour%20information.htm
Special Characteristics-Salty Taste


DO NOT TASTE
MOST MINERALS!
Example: Halite
http://mineral.galleries.com/scripts/item.exe?LIST+Minerals+Halides+Halite
Special Characteristics-Magnetism


Many iron minerals
will produce an
invisible magnetic
force field
“Lodestone” was
used by Vikings
more than 1,000
years ago as
compasses
http://www.minerals.net/mineral/oxides/magnetit/magneti4.htm
Minerals Links (NAGT)
An extensive listing of mineral links arranged by topic from the National Association of Geology Teachers (NAGT).
Minerals Links (University of Würzburg)
An extensive listing of mineral links including mineral descriptions and thin section images.
Minerals (Mineralogical Society of America)
The Mineralogical Society of America web site offers a good, general description of mineral properties, classification, etc. directed primarily
toward K-12 grade students.
Minerals (Trinity Mineral Company)
Beautiful photos of rare minerals offered for sale by the Trinity Mineral Company.
Minerals Information (USGS)
United States Geologic Survey (USGS) statistics and information on the worldwide supply, demand, and flow of minerals and materials essential
to the U.S. economy, the national security, and protection of the environment.
Minerals on the Internet
A wide variety of minerals-related sites sorted into relevant categories from Tasa Graphic Arts, Inc.
Mining and Mineral Resources
A great source for information about mining of mineral resources, mining news and trends, etc.
National Mining Association
The National Mining Association (NMA) represents the mining industry, mining equipment manufacturers, and other mining-related businesses,
throughout the United States.
Periodic Table of the Elements
In addition to listing a wealth of information about each element, this location also lists and describes numerous compounds.
Periodic Table of the Elements II
A great source for information on the elements.
Resource Fact Sheets (USGS)
United States Geological survey (USGS) activities in the natural resources theme area inventory the occurrence and assess the quantity and
quality of natural resources. Activities also include monitoring changes to natural resources, understanding the processes that form and affect
them, and forecasting the changes that may be expected in the future.
Resources from Space
University of Wisconsin course notes with links to several essays about resources from space.
Resource Sustainability
An essay that examines the future of Earth's resources.
Rock and Mineral Collecting (USGS)
Selected references on rocks, minerals, and gemstones from the United States Geological Survey (USGS).
Rockhounds Information Page
The Rockhounds Information Page offers many links to mineral and rock related Websites.
Smithsonian Gem & Mineral Collection
Images of mineral and gemstone specimens found in the Smithsonian Institution. (Not an official Smithsonian site)
Society for Mining, Metallurgy and Exploration, Inc.
The Society for Mining, Metallurgy, and Exploration (SME) is an international society of professionals in the minerals industry.
Society of Economic Geologists
The Society of Economic Geologists, Inc. (SEG) is an international organization of individual members with interests in the field of economic
geology.
State Minerals Information (USGS)
Statistics and information on the supply, demand, and flow of minerals and materials essential to the U.S. economy, the national security, and
protection of the environment from the United States Geological Survey (USGS).
Technical University of Clausthal
This site at a German university also shows some excellent mineral pictures.
Virtual Atlas of Opaque and Ore Minerals
This site provides over 400 full colour photomicrographs of the major ore-forming associations and opaque minerals in non-mineralized
rocks. It describes typical examples of each material from many classical localities throughout the world. For each association there is a
listing of the major (and important minor) primary ore minerals, alteration products and gangue, typical textures, a brief discussion of the
geology of the association and a list of references.
World Lecture Hall (University of Texas at Austin)
The World Lecture Hall features links to online courses in the United States and Canada.
Simplest to use for Mineral I.D. Lab:
Virtual Rock Bag
http://comp.uark.edu/~sboss/vrockbag.htm#minerals