Richard D. L. Fulton
Beneath the rolling hills of Hamiltonban Township, a township in Adams County, Pennsylvania, lies a land before time, a terrain that existed when even the first life upon Earth was just beginning to evolve into a myriad of more complex forms. Many of us know it as the ‘Grit Mill’ that is visible from Route #16 at Blue Ridge Summit, PA.
Some billion years ago, there was but one continent dubbed Rodinia. But continents—over the course of millions of years—tend to come and go, and 575 million years ago, Rodinia was about to drift away into the annals of time—literally. Rodinia was beginning to break apart into subcontinents due to continental drift.
Continental drift, resulting from the breaking up of continental plates—or even the collision of them—tends to generate the epitome of violent geological events, usually entailing massive earthquakes and/or the outbreak of severe volcanic eruptions.
The series of events resulting from the slow-motion demise of Rodinia, which impacted the geologic future of Hamiltonban Township, extended from South Central Pennsylvania through Maryland, and into Virginia. The sequence of events preserved in the rocks of that period has been dubbed the Catoctin Formation, according to the National Park Service.
Principally, this earthly disruption created fissures in the Earth’s surfaces in the above-noted region, allowing massive amounts of lava to flow out onto the surface, which, over time, hardened into a rock called basalt. But geophysics was not yet done with these hardened layers of basalt.
When the African plate collided with the North American plate around 250 million years ago, the collision, which crumpled up the land into mountains, exerted such intense force that it restructured many existing rocks into new forms…so much so, that it altered the basalt into a green, fine-grained form called metabasalt (meaning altered basalt). The effects of erosion over the course of millions of years weathered the mountains down, and within the Hamiltonban area, exposed the long-buried beds of metabasalt.
The first humans to dig into the ancient lava beds were those seeking native copper during the 1800s, which occurred in seams that subsequently formed within the Catoctin Formation via fractures within the rock. The long-abandoned mines can still be found in the Hamiltonban area, but most are far too dangerous to enter.
Then came Specialty Granules, LLC (SGI), a Hagerstown-based subsidiary of Standard Industries—in obviously more recent times—who began quarrying the metabasalt in Hamiltonban Township and pulverizing the rock to be used primarily in the production of roofing shingles. If one were to run their hand over one of these shingles, the rough surface granules one would feel are the particles of pulverized metabasalt (this weather-resistant rock helps prolong the life of the shingles).
Aside from the use in shingles, SGI also produces building materials and agricultural products using the metabasalt, according to Allison Devlin, senior communications and marketing specialist for SGI at their Hagerstown headquarters.
The Hamiltonban facility and quarry is known as the Charmian Plant, while the quarry itself has been dubbed the Pitts Quarry.
Matthew McClure, Specialty Granules vice-president of Roofing Operations, stated that the Hamiltonban metabasalt quarry operation initially began in 1923. McClure stated that the quarry is now some 1,500 feet wide from west to east and 2,000 feet wide from south to north, and that the operation mines the metabasalt deposit to a depth of approximately 400 feet.
The vice president also stated that the company mines approximately 1.5 million tons of metabasalt, annually, and that the metabasalt formation presently being quarried/mined should continue to be productive for 40 to 50 more years, “based on current mining volumes.” The company presently employs 160 individuals in conjunction with the Hamiltonban facility.
SGI is ”a leading mining and mineral processing company that specializes in the development of roofing products, building materials, and soil amendments for agriculture,” according to Devlin, further noting that SGI operates four nationwide surface mines, where it sources highly specific rock for its products, with the corporate headquarters and a fully equipped research and development facility, all located in Hagerstown.
And it all began… with the lost continent of Rodinia.
First miners at Pitts Quarry, 1930s.
Excavating metabasalt in Pitts Quarry.