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Glen Mills Quarry, Glen Mills, Thornbury Township, Delaware Co., Pennsylvania, USA

Biotite
Glen Mills Quarry, Glen Mills, Thornbury Township, Delaware Co., Pennsylvania, USA

Photo: M. Heintzelman
Extremely complex geology of Precambrian age. Series of interbedded greywackes and carbonates, along with graphitic gneiss and intermediate to dark igneous rock, folded and metamorphosed. The resulting rock types were then deformed again, and pegmatites were intruded, fracturing the total mass.

The quarry was first opened in 1884. In 1905 the General Crushed Stone Co. started operations and by 1976 was the largest quarry in the area at a depth of 300 feet. Although well below the elevation of nearby Chester Creek, water seepage is minimal.

Mineral List

'Allanite'
Almandine
'Apatite'
'Biotite'
Calcite
Diopside
Epidote
'Heulandite'
Microcline
Muscovite
Quartz
Schorl
'Stilbite'
Titanite
Zircon


15 entries listed. 10 valid minerals.

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References

Geyer, Smith, Barnes, Min. Col. Pennsylvania: 114-116.


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Copyright © Jolyon Ralph and Ida Chau 1993-2014. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of thousands of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
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