The 1,028 th meeting of 

The Mineralogical Society


Southern California



Program: What is a Pseudomorph

presented by: Erin Delventhal

Friday, August 9, 2024 at  7:30 pm.

See program notes below

Visitors are always welcome

About us…

The MSSC is a member of the California Federation of Mineralogical Societies and is dedicated to the dissemination of general knowledge of the mineralogical and related earth sciences through the study of mineral specimens.  We are a scientific non-profit organization that actively supports those endeavors through public outreach, field study and related programs.

For more information

Sign up for the MSSC Picnic and silent auction,  click here!

Chuckwalla National Monument BLM issued a Media Advisory that called a community meeting on management of Southern California public lands, namely H.R. 5660, the proposal to establish the “Chuckwalla National Monument”. The meeting was to be held this morning (6/14/24) in Indio, CA.  MSSC’s issue is similar to our involvement with the Mojave Trails National Monument and the rights to collect minerals, to rockhound and conduct educational field trips to students and others who share like interests.  If you were able to participate, thank you!  If not, and you  wish your voice be heard, I encourage you to review the paperwork sent to each of you this past Wednesday by MSSC’s Bulletin Editor Linda.  Write your comments and address them to Secretary Deb Haaland include CC’s to the Bureau of Land Management and to your local Congressional Representative:

U.S. Department of the Interior             BLM Calif Desert District DAC

Secretary Deb Haaland                           c/o Shelly Lynch, District Manager

1849 C Street NW                                    1201 Bird Center Dr

Washington, DC  20240                           Palm Springs, CA  92262

Notice of July 29, 2023 regarding Mojave Trails National Monument.  Reprinted with permission from San Diego Mineral & Gem Society.  Great commentary in the notice by its author, Lisbet Thorensen, SDMG’s Public Lands Representative.  Thank You, SDMG and Lisbet.  Angie Guzman, MSSC President.  Please click here to read article and commentary.

Program Notes: Friday, August 9, 2024 at 7:30, join us for “What is a Pseudomorph”.  Presented by Erin Delventhal.

Pseudomorphs have captured the attention of scientists and collectors for centuries, yet those who have delved into the study of these mineralogical oddities may have noticed a distinct problem: when the question “What Is a Pseudomorph?” is asked, the answer often seems to depend entirely on who is asked. This presentation does not seek to answer that question definitively but to provide an overview of how that question has been answered over time.

Western accounts of the history of the study of pseudomorphs often begin at the turn of the 19th century, when the term pseudomorph (Greek; pseudo = false, morph = form) enters the lexicon from René Just Haüy’s Traité de Mineralogie (1801). In an intriguing example of simultaneous invention, however, other authors concomitantly began to describe the same phenomenon. Afterkriſtalle (German; After = after[1]kriſtall = crystal), a term generally attributed to Abraham Gottlob Werner as it appears in the works of his students, appears as early as 1794 (Estner).

It is fitting that the story of pseudomorphs begins in disunity over what to call them, as the rest of the story continues in disunity about everything else: the definition of a pseudomorph, which classification scheme should be used for studying them, how they are formed, what should and shouldn’t be considered as a “true” pseudomorph, and so on – for some time, it was even debated as to whether pseudomorphs exist.

It is important to note that much of the literature concerning pseudomorphs known to the Western world is written in German, occasionally in French, and more recently in English. Many of these works have not been translated into other languages, rendering the study of the subject difficult. This record is also undoubtedly perforated by the absence of works in non-Western languages such as Arabic, Russian, Chinese, etc.

Though the study of pseudomorphs is rife with inconsistency and debate, investigation of these discrepancies provides an opportunity to question and redefine our understanding of what a pseudomorph is. The matter will not be settled today, but only further conversation can propel us towards an ultimate consensus: after all, no conflict can be resolved without understanding the disagreement.

[1] After can also indicate “no longer productive […] (expressing that something is false or fake):

Erin Delventhal grew up collecting minerals with her family – long road trips were punctuated with detours where she and her brothers could get dirty (and very tired) while collecting minerals.Photography and design took precedence as a hobby and a profession for many years, but a visit to the Tucson Gem & Mineral Show rekindled her love for minerals. She rejoined the mineral community with enthusiasm and has since been an active member in several organizations ranging from local to international, has been involved in mineral museums, symposia, and other educational programs, and has joyously returned to a life punctuated by getting dirty (and very tired) while collecting minerals. Among other things, Erin works as a freelance photographer, photo editor, and graphic designer.


MSSC members will be automatically on the invite list each month.

Non Members, you must request to attend the MSSC zoom meeting every month Email our Speakers chair, Carolyn Seitz at  no later than the Thursday before the scheduled meeting   Please include “ZOOM Meeting” in the subject line of your response. We will send you the meeting link.

Upcoming Events

all events, except field trips are via  ZOOM

  • September 13, 2024: TBA
  • October 11, 2024: Scott Braley
  • Board Meeting, Sunday October 27, 2024 at 1:00 pm, all are welcome to attend
  • August 24, 2024: MSSC Picnic-Technology Park, Caltec Campus 

The MSSC is pleased to offer the updated 2023 edition of Bob Pedersen’s X- Dana 

X-Dana Mineral Spreadsheet