Minerals

Dr. R. B. SchultzDr. 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:

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

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

HardnessGeologists rank minerals according to hardness using the Moh's

scale

Moh's Hardness Scale

1.0     TALC 2.0    GYPSUM 2.5 FINGERNAIL 3.0    CALCITE 3.5    COPPER PENNY 4.0    FLUORITE (Note the spelling!) 5.0    APATITE 5.5    STEEL KNIFE BLADE/GLASS PLATE 6.0    ORTHOCLASE FELDSPAR 7.0    QUARTZ 8.0     TOPAZ 9.0     CORUNDUM (RUBY) 10.0 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 “non-metallic”

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

CleavageTo 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