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                                                 Mineral of the Month--December


                                      Iron Sulfide




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Pyrite crystals, Arundel Quarry

Pyrite crystals, Arundel Quarry

Pyrite, Kurtz Quarry



by Ken Casey

Pyrite is found in many forms, mostly crystalline and massive.   Crystals range from pyrite cubes to pyritohedrons, and rarely octahedrons.  The massive variety can permeate rock as ore veins.  Crystals tend to form in limestone and lapis lazuli, for example, making for decorative building material and gem-quality rough for lapidary work.

pyrites.gif (1899 bytes)      pyritohedron2.gif (2002 bytes)       pyrite_sand_dollar2.gif (5424 bytes)

Often, fossils may be formed with pyrite as a constituent, such as those found in metamorphosed marine sediments.  Nature can create wondrous beauty from a simple iron sulfide, sculpting it into sand dollars, fern leaves, or sea shell replacements.

The pyrite family is composed of minerals that vary slightly from the typical iron sulfide chemistry, such as, chalcopyrite, which contains copper (CuFeS2).   Another variant is arsenopyrite, which has arsenic (FeAsS) in it's makeup.  Our most common form is called, just plain 'pyrite' (FeS2).  

Another name is "fool's gold", because it's shiny yellow, metallic luster resembles that of gold (Au).  A good field test to rule out gold as a candidate is to tap hard on a small, broken specimen with a rock hammer.  If it breaks, it is most likely pyrite.  If it flattens, it may contain gold, or copper.  The giveaway to copper's presence is it's brownish, or coppery, color.  Both gold and pyrite are associated with each other.

Other pyrite associations include: quartz, calcite, limestone, dolomite (from metamorphic rocks), and with other sulfide minerals, such as sphalerite and galena (from hydrothermal veins).

Sometimes pyrite is left behind by weathering, and leaves a characteristic cube-form laden in the surrounding rock.  A 'rusty' color may denote a 'pseudomorph' (false form) of 'limonite after pyrite'.  Limonite is essentially rusty iron.

Pyrite, and it's relatives, are found all around the world, perhaps on other planets.  We are fortunate to have several collecting locales in our area to find our own representatives of this shiny wonder.

On recent DMS fieldtrips, we have found nice specimens of the pyrite family.  To see them, visit the links below.

                                         More on Pyrite

Pyrite Slide Show, 11-20-2004 (IE)
Pyrite Slide Show, 11-20-2004 (N)

Arundel Quarry Field Trip, 3-13-2004
Kurtz Quarry Field Trip, 11-20-2004


Past Minerals of the Month

November Mineral of the Month: Stilbite

October Mineral of the Month: Celestite

All of the Mineral of the Month selections have come from most recent club fieldtrips, thus far.  If you have a suggestion for a future Mineral of the Month, please e-mail me at:, or tell me at our next meeting.

And Members, if you have pictures, or a story you would like to share, please feel free to offer.  We'd like to post them for our mutual enjoyment.

We are hoping for a possible tie-in to other informative programs that our fellow members might want to collaborate on.  Contact any officer or board member with your suggestions.


                    Photos by: Karissa Hendershot, Ken Casey
Drawings by: Ken Casey

This page last updated:  February 19, 2011 10:14:42 AM

Next Meeting

April Program, Monday, April 8, 2013:

"Destruction of the Fossil Exposures in the Chesapeake Bay Area" presented by Dr. Lauck Ward

General Club Meeting:
April 8, 2013

We are meeting at
Greenbank Mill

Special Meetings:

*Show Committee Meeting, April or May, 2013

*New Home/Lapidary Committee, 2013

*Board Meeting,  April, 2013

Next Field Trips


Past Fieldtrips

Next Show
DMS March Show
March 1-2, 2014 at DelTech Stanton


Our 2013 Show Theme was:
"All That Glitters is as Good as Gold!"

March Show 2013 Report






Fossil Forum

"Dinny, the Dino"

"Belemnites are coming"


MOTM June also commemorates our 50th Show!

It's shiny, yellow, and is a symbol of 50 Years!Can you guess?


Collecting Adventure Stories:

"Sunny Brook Crick Goethite" by Joe Dunleavy