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                    Mineral of the Month--October


                                          Lead Molybdate



                                          By Karissa Hendershot


Invitation to Members
Past Minerals of the Month

Some Wulfenite basics to get you started!






Red Cloud Mine, Arizona Los Lamentos, Mexico Geronimo Mine, Arizona


Wulfenite The name is in honor of the Austrian Jesuit mineralogist Franz Xavier von Wülfen (1728-1805).  It is a secondary mineral occurring in the oxidation zone of lead deposits, often as a pseudomorph after cerussite.

Wulfenite is an enigma in terms of its symmetry. There are conflicting results of various symmetry tests and this usually does not happen. It is either asymmetry of 4 or 4/m. The difference is the disputed existence of a mirror plane perpendicular to the four fold axis. If the mirror exists, then the crystals should have a top that is a mirror image of its bottom. Although most crystals don't show it clearly, the bottom pyramidal faces slant at a different angle from the top pyramidal faces. This demonstrates the symmetry of just 4. However, other tests of its symmetry show a 4/m symmetry. This symmetrical oddity only adds to Wulfenite's interest among serious collectors.



1.       Formula: Pb[MoO4],

2.       Color: red, orange, yellow, silver, white, and clear,

3.       Luster: vitreous,

4.       Transparency: Crystals are transparent to translucent,

5.       Crystal System: tetragonal; 4/m or 4,

6.       Crystal Habits include very thin square or octahedral pinacoidal plates with pyramidal faces truncating just the edges of the crystal. At times the pyramids become prominent and psuedo-dipyramidal crystal habits are seen, sometimes because of twinning. Prismatic faces are also seen and can make pseudo-cubic crystals. Also encrusting and cavernous aggregates due to intergrowth of crystal plates,

7.       Cleavage is perfect in one direction,

8.       Fracture is conchoidal,

9.       Hardness: 3,

10.  Specific Gravity: approximately 6.8 (very heavy for translucent minerals),

11.  Streak: white,

12.  Solvency: will dissolve slowly in acids,

13.  Associated Minerals include: mimetite, limonite, smithsonite, vanadinite and galena,

14.  Index of Refraction: 2.28-2.40 (very high, but typical of lead minerals),

15.  Best Field Indicators are crystal habit, color, density and luster,


Notable Occurrences for specific colors include:

·         The Bleiberg Mine in Austria yellow crystals,

·         The Primbram Mine in Chezch for gray crystals,

·         The Rezbanya Mine in Romania and the Red Cloud Mine in Arizona and the Congo for red crystals, and,

·         The Tsumeb Mine in Namibia and the lead mines in Phoenixville, PA for clear crystals.


Other great localities include:

  • Touissit Mine, Oujda, Morocco;
  • Rum Jungle, Northern Territory, Australia;
  • San Francisco Mine, near Cucurpa, Sonora, Mexico,
  • Ahumada Mine in Los Lamentos Chihuahua, Mexico, and
  • Chapacase Mine, Tocopillia, Chile.

     Until then, stay safe, and happy collecting. hardhat2a.gif (5709 bytes)


© 2005  All contributions to this article are covered under the copyright protection of this article
and by separate and several copyright protection(s), and are to be used for the sole purposes of
enjoying this scholarly article.  They are used gratefully with express written permission of the
authors, save for generally-accepted scholarly quotes, short in nature, deemed legal to reference
with the appropriate citation and credit.
  Reproduction of this article must be obtained by express
written permission of the author, Kenneth B. Casey, for his contributions, authoring, photos, and
graphics.  Use of all other credited materials requires permission of each contributor separately

Links and general contact information are included in the credits above, and throughout this article.
The advice offered herein are only suggestions; it is the reader's charge to use the information
contained herein responsibly.  DMS is not responsible for misuse or accidents caused from this
article. All opinions, theories, proofs, and views expressed within this article, and in others on this
website, do not necessarily reflect the views of the Delaware Mineralogical Society.

karissa.jpg (2366 bytes)

   About the Author:  Karissa is the current President of the Delaware Mineralogical Society.  E-mail:

Invitation to Members


Want to see your name in print?  Want to co-author, contribute, or author a whole Mineral of the Month article?  Well, this the forum for you!

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.   Of course, you get full photo and author credit, and a chance to reach other collectors, hobbyists, and scientists.  We only ask that you check your facts, give credit where it is due, keep it wholesome for our Junior Members watching, and keep on topic regarding rockhounding.

You don't even have to be experienced in making a webpage.  We can work together to publish your story.  A handwritten short story with a Polaroid will do.  If you do fancier, a text document with a digital photo will suit, as well.   Sharing is the groundwork from which we can get your story out there.

Our club's webpages can reach any person surfing the net in the world, and even on the International Space Station, if they have a mind to view our website!

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

November's MOTM will be a surprise.  For December 2005, we are waiting for your suggestions.  What mineral do you want to know more about?

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Most of the Mineral of the Month selections have come from most recent club fieldtrips and March Show Themes, and from inspriring world locales. 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.






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