Sunday, August 16, 2020



 Three of us headed from Baltimore in search of piemontite on a hillside near Hamiltonban Township in the South Mountain area of Adams County, Pennsylvania. We parked along Mount Hope Road near Gum Springs Road. If we were going to find piemontite  we knew it would occur in outcrops where reddish pink metarhyolite dominated. Soon we were following a trail along the base of the ridge.


Within a few minutes, we spotted some large boulders through the trees. Although no hint of a trail led to them, we bushwhacked about 20 yards uphill,  found the reddish pink metarhyolite we were looking for and soon spotted some piemontite. It occurs mostly in adamantine radiated microscopic prisms exclusively at or near where  quartz has intruded the metarhyolite. We believe we were in one of six known South Mountain area piemontite localities, at least four of which date from the 1890’s

We were also within about a quarter mile of seriously overgrown dumps from copper prospects dating back yet further into the 19th Century.  This was one of  about 20 known localities for native copper in the South Mountain area. Always found in volcanic metabasalts,  the copper was from deposits that were much smaller than but otherwise closely resembled the enormous and lucrative Keeweenaw deposit in upper Michigan. Although extensively prospected well into the 20th Century, the copper never proved plentiful enough to be viable.  

The South Mountain area has long fascinated geologists.  Their focus has always been less on the copper than  the geologic history exposed by rocks over hundreds of millions of years of  erosion.  Research regarding the  piemontite occurrences, while thorough and specific, was limited to separate studies. 

This region prominently straddles the Maryland line into Frederick County, where the geology is similar. The Pennsylvania side calls it South Mountain, Maryland calls it the Catoctins. Geologists have extensively studied the rocks on the Maryland side as well.  Nearly all the studies, however, have been specifically  limited either to Pennsylvania or to Maryland.

Some of the Pennsylvania studies at least acknowledged the presence of piemontite, even though sometimes referred to as “rusty epidote,” or "piedmontite."   In one of a series of articles entitled Chronicles of Central Pennsylvania Mineralogy, the late Jay Lininger described the phenomenon: "Like the comedian Rodney Dangerfield who didn't get no respect." In Maryland, piemontite got less than no respect.It has received no mention. 

Yet, piemontite has aesthetic qualities that make it a highly appealing mineral species as a member of the epidote group, like zoisite and allanite.  John Sinkankas in Gemstones of North America even listed “piemontite in rhyolite” as “semi-precious gem cutting material.” Its presence shows less weathering and better luster within freshly broken rock. Though usually in radiating microscopic crystals as described, a few specimens that are less common bear larger crystals up to about 15 mm. x 3 mm.  Nearly all such crystals have been fractured upon recovery. Seeing perfection is unrealistic. Piemontite is neither common nor highly valued relative to many other species, but regard for it is rising. .

A few years ago, this writer was working a booth at a show in the Towson, Maryland Armory. A man walked by with the most spectacular South Mountain piemontite specimen I’ve ever seen. I’m sure he intended to sell it, but he did not mention a price. After I complimented the specimen, he moved on. Had this happened today, I would happily have emptied my wallet.

Nothing short of synchronicity could make sense of how this writer personally collected piemontite in Maryland’s Frederick County only three weeks before our recent collecting trip. I was clueless that piemontite was in a specimen picked up in a field less than a mile down a road leading west from the tiny hamlet of New London.

 In typical fashion, I had stopped to check out some minor excavation and a small pile of rocks and dirt along the south side of the road.  Standing out among the rocks lying on the ground was the piece of pink metarhyolite pictured above at right.  Just as I knew that  metarhyolite of such color existed in Frederick County, I also realized how conspicuously misplaced it seemed compared to other surrounding rocks. So I picked it up and took it home. No thought of piemontite ever entered my mind. Upon arriving home, I threw it onto the rock pile in my back yard and never mentioned the find to anyone.

Three weeks later by sheer coincidence, a collector called and asked me to join him to look for piemontite in Adams County and write a post about it if we found any.  We went, we found piemontite, and it was obvious that the material in which we found it was the same as the piece I’d collected near new London. Doing my research, I read something in the aforementioned article by Jay Lininger that aroused my curiosity. The article stated that that the renowned late geologist Dr. Florence Bascom, in a her PhD thesis about piemontite,  proved that some of the pink colored rhyolites drew their color from included piemontite.I should mention that Dr. Bascom was the first woman in the United States to earn a PhD in geology and later went on to establish the Geology Department at Bryn Mawr University.

So I went out to the rock pile in the back yard and grabbed the metarhyolite I’d found near New London. A presence of piemontite was readily apparent. I did not report this as a new find for Maryland because it seemed quite obvious that the specimen was not indigenous to the field where I collected it.

However,  metarhyolite has an established presence just a few miles further west of New London  in Maryland’s Catoctins. As long a some of it is the same color as the  ubiquitous reddish metarhyolite on the Pennsylvania side of the state line, piemontite will very likely be present., Once uncovered and verified, it could be a legitimate new find for Maryland.    

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