Saturday, June 19, 2010

An All But Forgotten Maryland Gypsum Find

Among the most spectacular mineral specimens known to have been collected in Maryland are the blades and rosettes of gypsum (referred to as selenite when crystallized) that have been plucked from clay along the St. Mary's River banks at Chancellors Point and at Fort Washington in Prince Georges County beneath the bluffs of the Potomac. Lesser known, arguably more spectacular, and all but forgotten are crystals collected approximately 50 years ago from a deposit near Fort Foote in Prince Georges County about three miles down river from Fort Washington. For the second recent Sunday afternoon, a row, I had the opportunity to accompany Jeff Nagy on another drive to Virginia, this time to Strasburg for further research on his project to update and republish the 1981 Maryland Geological Survey publication Minerals of the Washington, DC Area by Lawrence Bernstein. Specifically, his mission was to meet and learn about the find from Gary Allard, who with his brother Brian, now deceased, had discovered the deposit.

For its year and a half of productivity, the site was the secret domain the two brothers. Gary appears in our title picture holding a rosette and the most spectacular crystal blade of the find, which is the largest crystal of selenite I've ever seen from Maryland. Amazingly, its appearance suggests that it could once have been part of a rosette. It is the same crystal that Gary was photographed holding 49 years ago in an article entitled Crystals by the Ditchful that appeared in the June-July, 1961 edition of Rocks and Minerals . At present, we are awaiting permission from Rocks and Minerals new publisher to post a reproduction of that earlier picture. If granted, one will be inserted herein soon thereafter.

Over less than two years, the two brothers pretty much cleaned out most of the crystals, using some for a science project at school and selling a others to classmates. Then they notified Ellsworth Swift,who authored the article in Rocks and Minerals. By then, the ditch had become less a source of crystals than what Swift referred to as "a challenge to discover the nature of the deposit and a chance to speculate on its formation."

He noted in the article that the Fort Foote crystals occurred in the Patapsco Clay, which also hosted other gypsum finds reported from the region. He described this clay as formed in the Cretaceous Age and variegated (in colour). Gary Allard recalled that the crystals occurred in a a "purplish" clay that was darker than the crystal bearing Patapsco clay at nearby Fort Washington. The crystals that Gary and Brian collected, whether rosettes or single crystals, were generally larger and less stained by clay than most of the better known material collected at Fort Washington and in St. Mary's County.

Particularly interesting was that while riverside bluffs had yielded the Fort Washington and St. Mary's crystals, those from Fort Foote were collected about a half mile inland in a ditch intended for drainage alongside what was soon to be paved over as an extension of River Bend Road. Just as noteworthy was their confinement to a 125 foot section of the ditch. Swift suggested that this could mean the crystals "concentrated along structural features such as joints," or that this particular deposit was "irregular in shape with the ditch merely cutting a cross section through the crystal patch.'" He explained further how the crystals were most likely formed when groundwater from the Piedmont that contained sulfuric acid from decomposing pyrite flowed eastward and mixed with the lime bearing beds of the Coastal Plain at Fort Foote.

Gary Allard now lives in the Shenandoah Valley near Strasburg, Virginia. He said he moved there because it had more kinds of rocks than than "that boring Coastal Plain" where he grew up." He still loves to collect minerals and prior to his recent retirement was a jeweler and metal engraver. One of his recent finds that amazed Jeff and me was the green quartz crystal pictured at right from near Front Royal in Warren County, Virginia. The book Minerals of Virginia, by R.V Dietrich, 1991, noted nothing like it from Warren County. The only green quartz the book mentioned was presumably massive and from another part of Virginia with coloration "probably due to included amphibole or chlorite." It too, Gary discovered along the side of a dirt road albeit not in a ditch.


  1. Sadly, my childhood friend Gary Allard passed away from cancer earlier this year (2012). Gary shared his find with my brother Tom and me, and I still have a copy of that January-February 1961 Rocks and Minerals magazine with Ellsworth R. Swift's article. The selenite gypsum crystals I collected back then are in a display case in my living room.
    Peter Beck (The magazine misspelled our last name.)
    Accokeek, Maryland.

  2. Hello.

    My name is Sebastian Gargal, from Spain, I have found few similar crystals here in Spain. The only difference is my crystals are from 1 inch to 25 inches and very, very transparent. If you are interested please contact me at
    Best regards.