Buried Secrets: The Geological Significance, Formation and History of Iron Ore Deposits in the New Jersey Highlands

July 29, 2023
Group looking down at a old mine in New Jersey

Buried Secrets QUEST teachers examine a flooded iron mine entrance near Ogdensburg, NJ where Thomas Edison’s “New Jersey and Pennsylvania Concentrating Company” operated from 1891-1900. The orientation of the ore, and the mine, generally follow the trend of the metamorphic foliation. At its peak, the workings employed almost 500 workers, but was a financial failure. Thomas Edison did have a few other successful ventures, of course!

In the 18th and 19th centuries, over a hundred mines in Precambrian rocks of the Highlands made New Jersey (NJ) a major U.S. iron producer. This activity drove local economies, spurred settlement of the region, and helped fuel the industrial revolution. Buried Secrets, developed and led by Professor Blair Schoene, Lab Manager Laurel Goodell, and Research Specialist Isabel Koran, engaged participants in exploring fundamental questions related to the formation and age of this iron ore.

The teachers were introduced to New Jersey geology, rocks and minerals and plate tectonics. This included a presentation by Dr. Pierre Lacombe of the USGS (retired) on historical aspects of the mining. They embarked on a field trip to the NJ Highlands, where they hiked past flooded mine entrances and the remnants of Thomas Edison's mining complex near Sparta, NJ, that once employed hundreds of workers in a completely deforested landscape and completed transects across the now reforested bedrock.

They used their field measurements to discover they had mapped a bedrock structure that could be interpreted as a several kilometer-scale fold. Next, teachers examined textures in ore samples and experimented with igneous intrusion models, which indicated an igneous origin for the ore bodies that must post-date metamorphism. Finally, teachers learned about absolute dating, toured Professor Schoene’s high-precision Thermal Ionization Mass Spectrometry (TIMS) laboratory and evaluated data that confirmed the post-metamorphic timing of ore emplacement.

As a result of their Buried Secrets experiences, participants made significant gains in understanding the geology of New Jersey and the processes that occur at plate boundaries. They also benefited from exposure to the interdisciplinary toolkit of fieldwork, experiments, modeling, and lab analyses that geoscientists use to address scientific questions; perspectives that they will be bringing back to their own classrooms.

Funding was provided by NSF, Princeton’s Program in Teacher Preparation and The Department of Geosciences

Written by Laurel Goodell, Academic Lab Manager