|Latitude & Longitude (WGS84):||40° 45' 59'' North , 77° 6' 48'' West|
|Latitude & Longitude (decimal):||40.76650,-77.11341|
|Köppen climate type:||Dfa : Hot-summer humid continental climate|
National Limestone Quarries' main quarry, headquarters, and processing location. Excellent locality for calcite crystals, both clear, and orange in color, tan-colored dogtooth calcite, deep purple fluorite in dark gray limestone and purple fluorite in white massive calcite matrix, minor occurrances of pyrite, minor drusy quartz crystals, occasional occurrances of strontianite, and most importantly, and unique to this location, beautiful golden and white calcite travertine (flowstone) from a collapsed cave, which was uncovered on the north side of the main pit during the quarrying operations a few years ago. Some of the flowstone specimens contain rare helictite formations, and others contain crinoid fossils, incorporated right into the flowstone, and many complete stalactites and stalagmites have also been found, as well as crystallized, rippled and layered flowstone, suitable for slabbing and polishing. The flowstone fluoresces pale blue under SW UV light.
Perhaps this may be the only opportunity to collect specimens from this type of cave formation, since collecting in existing caves and caverns is illegal and unethical. Each year, crews continue to uncover more cave features and flowstone as quarrying continues.
This quarry is accessible to EFMLS-affiliated mineral clubs only, for group field collecting trips, from April thru October.(along with their smaller quarry in nearby Mt. Pleasant Mills, famous for clear calcite crystals of large sizes, strontianite, and their world famous wavellite on fossil bearing matrix).
(Note: The Google Maps address to the quarry is incorrect. The correct address is 3499 Quarry Road, Middleburg, Pennsylvania.)
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
6 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
252.17 - 541 Ma
|Paleozoic sedimentary rocks|
Age: Paleozoic (252.17 - 541 Ma)
Lithology: Sedimentary rocks
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
|Devonian - Silurian|
358.9 - 443.8 Ma
|Keyser and Tonoloway Formations, undivided|
Age: Paleozoic (358.9 - 443.8 Ma)
Stratigraphic Name: Keyser Formation; Tonoloway Formation; Coeymans Formation; Rondout Formation; Decker Formation; Wills Creek Formation
Description: In descending order: Keyser Formation--medium-gray, crystalline to nodular, fossiliferous limestone; upper part laminated and mud-cracked; not present east of Harrisburg; passes into lower Coeymans, Rondout, and Decker Formations in the east. Tonoloway Formation--medium-gray, laminated, mud-cracked limestone containing some medium-dark- or olive-gray shale interbeds; lower part passes into Wills Creek Formation east and south; passes into Bossardville and Poxono Island beds in the east.
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.