Pyrite - More Than a Fool's Folly
A Mineralogy Webpage Project
by
Jennifer Banta
Table of Contents
- Introduction
- Physical and Chemical Properties
- Pictures of Crystal Habits
- Sulfide Class Information
- Polymorphism of Pyrite
- Pyrite Group of Minerals
- Alteration
- Mining and Uses
- Pyrite's Role in WWII
- Print Resouces
- Electronic Resources
- Additional Links
- About Author
- My childhood is filled with memories of vacations to Colorado. My family would stop at
every rock and mineral shop we could find. Eyeing all the amazing specimens, I would also
gravitate toward one specific mineral, pyrite. Every place we stopped I would beg my dad to
buy some of those gold nuggets. In my imagination I dreamed of going on mineral and rock hunts
and returning with a fortune and pyrite sure looked like a fortune to me. My father asked me
why I wanted so many samples of the same thing, so I told him. After he stopped chuckling,
he informed me that what I had collected wasn't gold, it was fool's gold. "It just looks
like gold but it's really pyrite. Sorry, honey it isn't worth a fortune," he told me.
That's ok as I did not listen to him anyway. I not the fool, because to me pyrite was a treasure.
- My childhood fascination with pyrite has grown with me and is now an adult interest. This interest has led me on a fact finding mission to try and discover all I could about my treasure.
Return to the top.
Physical and Chemical Properties
Associated Minerals: calcite, fluorite, galena, gold, sphalerite, quartz and many more
Chemistry: Iron Sulfide, FeS2
Cleavage: Poor
Compostion: Iron 46.55% and Sulfur 53.45%
Color: Brassy Yellow
Class: Sulfides
Crystal Habits: Cube, octahedron, pyritohedron and a combo of the three, striated, drusy, stalactitic, interpenetration twins - called iron crosses, also found in nodules - flattened nodule called "Pyrite Suns" or "Pyrite Dollars", massive, reniform, can replace other minerals and fossils causing pseudomorphs
Crystal System: Isometric or bar 3 2/m
Density: 5-5.02 with 5.01 being the average for metallic minerals
Environment of formation: Hydrothermal, magmatic, metamorphic and sedimentary
Field Indicators: brittleness, crystal habits, hardness, streak and luster
Fracture: Conchoidal
Group: Pyrite group of Minerals
Hardness: 6.5
Luminescence: None
Luster: Metallic
Name Origin: Greek, pyrite's lithos meaning "stone which strikes fire," in reference to the spark produced when iron is struck with a piece of pyrite
Notable Occurrences: USA, Peru, Germany, Russia, Spain, South Africa and many others because pyrite forms in many differing environments.
Specific Gravity: 5.1+
Streak: Greenish black
Synonyms: Cobaltian Pyrite, Fool's Gold, Iron Disulfide, Nickelian Pyrite
Transparency: Opaque
Uses: Minor ore of sulfur to make sulfuric acid, also used in jewelry called "marcasite," and sold as mineral specimens
Other Characteristics: Unlike malleable gold, pyrite is brittle; when a pyritohedron of pyrite is crossed with a cube, striations occur on the cubic facesReturn to the top.
Pictures of Crystal Habits
Cubic habit of pyrite.
Image taken from:
http://www.minerals.net/minerals/
sulfides/pyrite/pyrite1.htm
Pyritohedral pyrite crystal.
Image taken from:
http://www.minerals.net/mineral/sulfides/
pyrite/pyrite2.htmReturn to the top.
Sulfide Class Information
- Pyrite is classified as a sulfide. Sulfides contain a metal cation, Fe in pyrite's case, and a sulfur anion. A majority of economically important ore minerals are sulfides. Copper, cobalt, silver and lead are other examples of sulfides. Sulfides tend to be opaque, have high densitites, have distinct colors and streaks. Pyrite has a distinct brassy yellow and a distinct greenish-black streak. Sulfides are generally found in hydrothermal vein deposits, as dispersed elements, igneous origin or as secondary replacements. Sulfides tend to be polymorphic.
To learn more about sulfides check out http://mineral.galleries.com/MINERALS/sulfides/class.HTM.
Return to the top.
Polymorphism of Pyrite
- Pyrite and Marcasite are polymorphs because both have the same chemical formula, FeS2, but both have different atomic structures. Differing atomic structures lead to differing symmetries and differing crystal shapes. Pyrite has an isometric, cubic structure with covalently bonded S2 pairs. Pyrite's structure is compared to that of halite, NaCl, with Fe in the Na position and S2 in the Cl position. Marcasite on the other hand is orthrohombic structure. Marcasite tends to form over a range of low to medium temperatures in sedimentary rocks and metalliferous veins. Pyrite can occur at higher temperature magmatic sites as well as marcasite's temperature range.
Return to the top.
Pyrite Group of Minerals
- Minerals with similiar isometric structure and related chemistry are grouped together. The pyrite group as named for its most common member, pyrite. The general formula for minerals in this group is AX2. The A can be zinc, iron, mercury, gold, cobalt, copper, manganese, nickel, osmium, iridium, palladium, platinum or ruthenium. The X can be sulfur, arsenic, antimony, bismuth, selenium and/or tellurium.
To learn more about the pyrite group of minerals and view a list of their names connect to http://mineral.galleries.com/MINERALS/sulfides/pyrite.HTM.
Return to the top.
Alteration
- Pyrite can be altered to an oxide of iron, becoming limonite. Although pyrite is more stable than marcasite, pyrite is easily oxidized. Veins of pyrite are commonly found with overlaying cellular deposits of limonite called gossan. The ready oxidation of pyrite both disintegrates and stains any pyrite containing rocks, making them ineffective for any structural purposes. This serves to limit the use of pyrites iron content.
Return to the top.
Mining and Uses
- In olden days, Native Americans used to carve and polish pyrite for use in mirrors. Today pyrite is sometimes mined because of its association with gold and copper. Pyrite is also mined for its large sulfur content. The sulfur is then used to manufacture sulfuric acid and copperas. Copperas, ferrous sulfate, is used in dyeing, in the manufacturing of ink, as a wood perservative and as a disinfectant. Cut as a gemstone, pyrite is usually sold under the name marcasite. Jewelry makes can use pyrite but its brittle nature and ability to powder easily limit its use.
Return to the top.
Pyrite's Role In WWII
- During WW II, the demand for sulfur kept increasing while the amount of native sulfur mined in North America kept decreasing. Native sulfur mines were becoming exhausted, making pyrite an attractive alternative economically. One large deposit near Ducktown, Tennessee began mining pyrite, pyrrohite and pentlandite exclusively for their sulfur contents. Sulfur is needed industrially for the production of sulfuric acid. Since then new production methods for sulfur have been produced but at that time pyrite's sulfur content saved the day.
Return to the top.
RESOURCES
Printed Resources
- Klein, Cornelis and Hurlbut, Cornelius S. Jr. Manual of Mineralogy. 21st ed, rev / after James D. Dana. New York. Pub. by John Wiley & Sons, Inc. 1999.
Electronic Resources
- The Mineral Pyrite. Amethyst Galleries.
http://mineral.galleries.com/MINERALS/sulfides/pyrite/pyrite.HTM > 1996. Pages 1-2. Access date 10/17/01.The Pyrite Group of Minerals. Amethyst Galleries.
http://mineral.galleries.com/MINERALS/sulfides/pyrite.HTM 1996. Page 1. Access date 10/17/01.- The Sulfides Class. Amethyst Galleries.
http://mineral.galleries.com/MINERALS/sulfides/class.HTM1996. Page 1-5 Access date 10/17/01.- Barthelmy, D. Pyrite. Mineral Database.
May 25,2001 Page 1-4. http://webmineral.com/data/Pyrite.shtml Access date 10/17/01.Additional Links
Pyrite http://webmineral.com/data/Pyrite.shtml
The Mineral Pyrite: http://www.minerals.net/mineral/sulfides/pyrite.htm
Mineral Description Pyrite: http://www.geology.neab.net/minerals/pyrite.htm
PYRITE Chapter 21. Sulfides, arsenides, antimonides, and sulfosalts: http://simplethinking.com/dunn/ch21/pyrite.stm
About Author
I am a student at Emporia State University. This webpage was made as an assignment for completion of a mineralogy course. The facts on the mineral pyrite and all information can be verified by connecting to the electronic resource links or reading the print reference. Thanks for taking the time to view my page. If you have any questions or comments you can email me at JenBant@netscape.net.
Created 29 November; updated 3 December, 2001.
Return to the top or to the student webpages.
- My childhood fascination with pyrite has grown with me and is now an adult interest. This interest has led me on a fact finding mission to try and discover all I could about my treasure.
Introduction