New Jersey

Geology

Geological Development of Franklin and Sterling Hill Minerals

Billions of years ago, Earth began as a mixture of molten metals and slag that eventually cooled with a crust enveloping its surface. The dense molten minerals moved toward the center of the smoldering globe by gravity. And successive shells of slag formed and solidified, each with varying composition, in a layered arrangement. Through convection, molten materials containing metallic elements moved out at certain points, cooled over a period of millions of years, and finally deposited as minerals in the outer crust. These deposits contain appreciable quantities of metal-bearing minerals known as orebodies.

One billion years ago, the most unique deposits of zinc ore in the entire world were created in the Franklin/Ogdensburg area in New Jersey. Ore deposits containing more than 345 mineral species - 35 found nowhere else on the surface of the Earth - all of which, mineralogically speaking, are true wonders of nature.

"It's an enigma… how it got here in the first place. It's like trying to solve a murder mystery when all the witnesses are dead," explained Richard Hauck, president of the board of directors for the Sterling Hill Mining Museum in Ogdensburg. "There are a number of theories, but not one of them adequately explains how these mineral deposits got here."

"These orebodies were created more than 1.1 billion years ago," added John Cianciulli, curator of the Franklin Mineral Museum in Franklin. "We think a series of geological events took place - sedimentation, igneous injection, geological metamorphosis, volcanic activity - all combining over millions of years to create this unique deposit."

More than 15,000 years ago, in the Pleistocene Ice Age, the area was covered by a major ice sheet called the Wisconsin Ice Sheet, which eventually retreated, shaped and formed the area's topography of bedrock, rift deposits and bodies of water.

As the glaciers retreated, they exposed portions of the orebodies known as "outcroppings." The glacial exposures of the orebodies permitted groundwater to infiltrate, causing oxidation and resulting in the formation of even more mineral species.

The great mineral wealth created not only an economic engine for the area for more than 100 years, but also a classroom, found nowhere else on Earth, where scientists and researchers could study so many minerals in one place.

"Minerals and mining have been important to human development from the beginning," Hauk declared. "Name one product made by man that didn't require mining in it's production - there isn't one. This science translates into applications, like lasers. Lasers were made possible by using simple rubies."

"The open pits allow the student of geology to see every phase of geological development," Cianciulli explained. "You can see igneous, sedimentary and metamorphic assemblages. You can see folding and faulting. There are very few places on Earth like this. This area has been the world's classroom of geology for more than 100 years."

While mining brought people to the area in the first place, it was the discovery and abundance of fluorescent minerals that has excited and attracted scientists, educators and collectors ever since.