PIEMONTITE NEAR CULP RIDGE PENNSYLVANIA AND NOW IN MARYLAND!

 

 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 19^th 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 20^th 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.    

Bounty of Baltimore County's Texas Quarry

Look  to the right heading north on I-83 between Padonia and Warren Roads. Where not obscured by embankment, you glimpse the enormous Texas Quarry. As one of five Maryland aggregate quarries that Bluegrass Materials purchased in 2014 from LaFarge North America, this ever growing pit has yielded dolostone for various purposes since well before the Civil War. Its length extends for a mile in places, and it penetrates the Cockeysville Marble formation to a depth of more than 500 feet, well below sea level. Over time, it has yielded a range of mineralogically interesting material, most that was collected decades ago ,

Arguably, the Texas Quarry is best known for its dravite, a tourmaline species, which occurs as adamantine crystals in white dolomite and calcite. The above specimen is from the collection of John S. White, past Curator-in-Charge of the Gem and Mineral Collection at the Smithsonian.

Despite its place in the Mica Group, phlogopite can visually resemble dravite. Sharing similar color and adamantine luster,  phlogopite is ubiquitous at the Texas Quarry. The above pictured piece could be the most collection-worthy Texas Quarry phlogopite piece  known to exist. It is a true Maryland classic that was pictured in  Ostrander and Price's Minerals of Maryland (Natural History Society of Maryland, 1940), and is currently owned by Baltimore area collector Bob Eberle.

Scapolite Group species and varieties, often simply labeled as wernerite, have always been a special find. Regardless of nomenclature, if the color is lilac, it's  a Texas Quarry treasure. We acquired the above pictured specimen from the late Baltimore County dealer and collector Larry Krause. The historic Natural History Society of Maryland label that accompanied it noted that it was collected by the late Charles Ostrander, co-author of the aformentioned book.

Never plentiful, most Texas Quarry Scapolite Group material featured greenish gray crystals. This 4.3 cm. crystal is a fine example. Particularly impressive is the pinkish lavender fluorescence of the accompanying calcite.

Relatively little Texas Quarry calcite fluoresces..As attractive as the above specimen appears, we've observed little  to be as  collection worthy as crystals from other well- known Maryland localities.

Rutile in crystals of more than a few centimeters are rare. The well-known Maryland collector Fred Parker collected this 1.6 cm. long crystal in the 1990's

Neither sphalerite nor baryte are particularly common here.  However, they are  notable when associated with each other as shown above along with some dolomite in the mix.

Little if anything relating to the occurrence of  bornite is in any of the literature we've been able to access. Nor has there been mention of chalcopyrite. That Fred Parker's sharp eye spotted this bornite specimen does not surprise us. We managed within a few seconds to observe chalcopyrite in dolostone boulders piled up near the Bluegrass Texas Quarry sign when shooting our title picture.  

The chalcedony in calcite, as pictured above proved to be eminently collectible.

We saved the image of Texas Quarry  pargasite for last.  Another Fred Parker find, it is the only example of this species of which we are aware from  the Texas Quarry or any other locality in Maryland, except for the Hunting Hill Quarry in Montgomery County.

Other species known to occur at the Texas Quarry are as follows :pyrite, tremolite, pink dolomite, wollastonite, fuchsite, purple fluorite, dendrites (probably manganese oxide), galena, pyrrhotite, quartz, sphene, talc, chlorite, molybdenite, margarite, diopside, and asbestos.

AFTERWORD

Before posting  we contacted Fred Parker in New Mexico to conifrm that he had not only provided but  personally field collected the pictured bornite, rutile, and pargasite as noted.. After confirming this, he shared two facinating remembrances

• A specimen from a find circa 1935 labeled "sphalerite on limestone." 

Associated with dolomite crystals,they are stacked hexagaonal plates that appear to be sphalerite. I believe these are sphalerite after wurtzite paramorphs and good ones at that. Fred recalled  where this specimen was housed when he observed it. If still in the same collection and access can be arranged, we'll cover it in a subsequent post. 

• AMAZING  DRAVITE 

I also recall in the early-mid 1990's a blast in which a boulder at the base of the rubble pile contained the best dravites I ever saw from Texas, as I recall 3 to 4 inch crystals. They could not be safely recovered so went to the crusher. 

Minerals of the Greenspring Quarry in Baltimore County, Maryland

Since 2006, the 40 acre former Arundel Greenspring Quarry has been the centerpiece of  Quarry Lake at Greenspring, a thriving gated community comprising about 500 condominiums and 100 single family homes served by 335,000 square feet of office,  retail, and restarurant space. The water within fills a hole  from which over the course of more than a century, 350 tons of Cockeysville Marble have been removed. It is the deepest water in Maryland.

Prior to  closing in 1999, the quarry was an occasional destination for field trips by the Baltimore Mineral Society and other groups. It was known as the McMahon Quarry when Charles Ostrander and Walter Price described it in the Natural History Society of Maryland's 1940 publication Minerals of Maryland. They mostly reported species one might expect to find in the Cockeysville Marble.

In later years,  a significant find of pale blue fluorapatite such as shown at left, attracted the attention of  and became prized by  local mineral collectors. Many of them may have been unaware of  material such as  Pennsylvania collectors Joe and Jean Dague uncovered at the quarry during the late 1990's.

While the  Mineral Bliss post of Jan.20, 2012, entitled An Amazing Visit with Pennsylvania's Joe Dague focused on remarkable finds from the Dague's home state, a major purpose of the visit had been to see material they had collected in Maryland.  While there, I  acquired several flats of their Maryland minerals.

Those flats included not only species for which the Greenspring Quarry was known, but plenty more. Somewhere in all that  Cockeysville Marble, the Dagues unearthed some rich pegmatite. The Greenspring Quarry pieces from those flats are pictured below.   We suspect that some of the specimens could WOW not only many in the local mineral collecting community, but perhaps current denizens of Quarry Lake at Greenspring as well.

                                                       BERYL (var.)AQUAMARINE

                                                      GARNET and SCAPOLITE

PYRRHOTITE

SHORL

MUSCOVITE

ALBITE

Feldspar Mining in Maryland

Pictured above at the long abandoned Tunnel Feldspar Mine in Howard County, are Maryland Park Service Supervisor for Patapsco Valley State Park Michael Burditt and Jeff Nagy. The latter's work continues regarding an updated revision of the 1980 Maryland Geological Survey publication Minerals of the Washtington, D.C. Area. Nagy located the Tunnel Mine by first researching literature written in the 1920's at the Maryland Geological Survey. Later, he reached the site after assuming that what today is a driveway appeared as "Tunnel Road" on a 70 year old map. The 1940 Natural History Society of Maryland publication Minerals of Maryland by Ostrander and Price also mentions the Tunnel Mine.  Noted is  how the adit "cuts into pegmatite rich in white potash feldspar." Located less than a mile into Howard County beyond Marriottsville, it is on land that the State of Maryland leases to active present farming interests. 

The adit leads into a water-filled tunnel about 150 yards to the left as one heads up the driveway. Nagy does not know how far back it leads. Minerals of Maryland reports the occurrence of "white cleavage microcline, microcline crystals, a little mucscovite, biotite, and black tourmaline" at the mine.  In the mica schist close by, were reported kyanite, staurolite, garnets, limonite psueudomorph after pyrite, and quartz crystals." Nagy has also perused literature from the U.S. Geological Survey citing  the Tunnel Mine as a locality for beryl. But today, vegetation has long covered any dumps that may once have been, and the face of the cliffs near and surrounding the adit show little to attract collectors. 

Interestingly, the available literature (unless we have missed something) shows the Tunnel Mine as Maryland's only feldspar mine.  Less than a mile away, however, about hundred yards upstream from Marriottsville along the Carroll County bank of the Patapsco, is an adit leading into what obviously  was another feldspar mine. The Maryland DNR Trail Guide has even mapped this  adit as a cave. Water has not invaded it. Nagy ventured  inside  in 2010 with Maryland collector Fred Parker and a reporter from NPR  to broadcast a story about the mine's existence. Nagy recalls the opening reaching back approximately 300 navigable feet. 

Based on  personal visits to both localities, as well as input from Jeff Nagy and Fred Parker, the likelihood of finding collectible minerals at either locality is slim at best. Regardless, laws prohibiting collecting  in the Patapsco Valley State Park are rigidly enforced. Breaking them entails  theft of State property.  Access to see the Tunnel Mine would require permission  from the active farmers who rent the land as well as the Maryland Department of Natural Resources.  The adit along the banks of the Patapsco near Marriottsville Road, however, is accessible to the curious, all the more so during seasons when the surrounding vegetation is minimal.