Curious about the world under your feet?

Join with us to explore

the earth's 4000+ minerals and how they came to be!


Mission of the Mineralogical Society of the District of Columbia (MSDC)

  • To learn together and further knowledge about mineralogy and earth sciences
  • To share the pleasure of collecting minerals
  • To welcome you to explore these interests with us

Who We Are

  • We're rockhounds, professional mineral scientists, mineral collectors and enthusiasts, and people with new interests in minerals and earth sciences.
  • We're from DC, the Maryland and Virginia suburbs, and points beyond.
  • You're always welcome!

What we do:

  • Since 1942, we've met at the Smithsonian Institution to discuss all facets of earth sciences and hear  from experts in many related fields.
  • We sponsor or join with other local clubs for field trips.
  • Our monthly newsletters offer diverse articles at all knowledge levels.
  • We support mineral sciences by volunteering at the Smithsonian and elsewhere and by finding other ways to expand interest and knowledge.

When and Where

  • 1st Wednesday of every month except July and August.
  • At the Smithsonian National Museum of Natural History (NMNH), 10th Street and Constitution Avenue NW, Washington, DC.
  • 7:30 p.m. in the Constitution Avenue lobby. A security officer leads us to our meeting room, so please be on time.
  • December time and place may vary.

Next field trip and meetings – everyone welcome!

Mar. 7 meeting - Garnets with John Weidner - sure to be educational and fun!


March 7, 2018 Program – GARNETS!

NOTE: For tonight only, there will NOT be optional dinner together before the meeting.

There are not many minerals that can be found in both metamorphic and igneous environments, but garnet is one mineral that is found in both.  Except garnet isn’t really one mineral.  It’s a whole family consisting of many varieties – andradite, grossular, pyrope, spessartine, melanite, uvarovite, tsavorite, topazolite, and many others.  And garnets are found in all colors.  It used to be said that garnet could be found in every color except blue.  But a few years ago, blue garnets were found in Madagascar!  Turns out they are a blend of spessartine and pyrope.  How does that happen?  In what ways are the different varieties different?  In what ways are they the same?  Just what is it that makes a garnet a garnet? 

Our presenter this month, John Weidner, will address many of these questions and enlighten us on the topic of garnets.  John is an active MSDC club member and is also the club’s treasurer.  John completed his PhD in math in 1973.  Since then he has alternated between teaching math in college and designing databases as a subcontractor.  He is presently a registered volunteer with the Geology Department at Northern Virginia Community College (NVCC) and promotes interaction between NVMC and MSDC.  Last year, he set up “thin section” workshops at NVCC and has done so again this year, with two “thin section” workshops coming up in the next month. 


Be forewarned, John’s presentations often involve audience participation.  In his presentation last year on neosilicates, John had us on our feet performing the dance of the tetahedrons.  For his garnet presentation rumor has it that there may be a song (in 4/4 time).   

Please join us in taking John to dinner on March 7th before the club meeting.  We will be meeting at 6:00 pm at Elephant & Castle Restaurant, 1201 Pennsylvania Ave, NW, Washington, DC, about 2 blocks from the Smithsonian Institution National Museum of Natural History (NMNH) where our club meeting is held.  If you cannot make it to dinner, we will meet in the NMNH lobby at 7:30 pm and head up to the Cathy Kerby Room for John’s presentation.


March 24 and 31 - Thin Section Field Trip 

  • Polish a rock.
  • Glue it to a microscope slide.
  • Cut it off at about a thousandth of an inch.
  • Look at it through a polarizing microscope.
  • You are looking at a thin section, a research tool in geology for over a hundred years, and a way to make amateurs like me say “Wow!”
  • Like to look at some?
  • Come to the Thin Section Field Day, at the Annandale Campus of Northern Virginia Community College, March 24 and March 31.
  • More info to follow.
  • If you plan to come, please RSVP to jfweidner at gmail dot com, so we know how many people to prepare for.

April 4 - Recent Smithsonian mineral and gem acquisitions with Dr. Jeffrey Post, head of the Smithsonian Mineral Sciences Department and gem collection

May 2 - Poland's Wieliczka Salt Mine with Denise Nelson

June 6 - Dr. Lance Kearns of the James Madison Geology and Environmental Science Department -- topic not yet announced

Want to know more about any of this?

  • Email us at thompson01 at erols dot com. We’re happy to answer your questions.

  • Check the MSDC newsletter.

  • Visit a meeting any time!