Although the east coast of the
United States is not thought of by many as a mining area, it
has been a substantial producer of metals in the past and upstate
New York continues as a major mining district. Ore deposits in
this region occur within the high-grade metamorphic rocks of
the Grenville terrane. Fourteen graduate students and two professors
(Murray Hitzman and Eric Nelson) spent a week in October, 1999
visiting these base metal and industrial mineral deposits.
The field trip began with a flight from Denver to LaGuardia airport
and an escape from New York City to the beautiful rolling, rural
countryside of northwest New Jersey. The first visit was to the
Sterling Hill zinc mine which is currently an industrial museum.
The Sterling Hill and nearby Franklin Furnace deposits are world
famous for their mineral assemblage which is dominated by zinc
silicate minerals such as willemite and franklinite. Mr. Robert
Metsger, former chief geologist of the mine, lead the group on
a tour of the underground workings and open pit. The tour was
followed by an exercise along one of the underground drifts where
students split into groups and geologically mapped the complexly
deformed orebodies. Because willemite and several of the other
minerals with the ore fluoresce under ultraviolet light, mapping
was conducted in part by UV lamping.
Following a drive north through Pennsylvania and New York, the
group was given a superb lecture on the geology of the Balmat-Edwards
zinc orebodies by the mine staff. The next day we visited one
of the Balmat orebodies underground and then visited the nearly
exhausted Pierrepont orebody. These sphalerite orebodies occur
within highly deformed, high-grade metamorphic rocks, dominantly
marbles but including a thick anhydrite (evaporite) layer. Underground
exercises forced the students to try and decipher the multiple
folding events which have affected the ores.
The following day we drove to the heart of the Adirondack Mountains
which were at the height of autumn color. The students first
examined the Sanford Lake titanium deposit, a classic anorthosite-related
deposit. We then moved on to the Barton Mine on Gore Mountain.
Garnets have been mined at Gore Mountain for over a century.
The deposit is spectacular with nickel- to basketball-sized garnets
in amphibolite-grade gneisses. The red-brown garnet from Gore
Mountain is familiar to anyone who has used sandpaper (the red-brown
sandpaper is made from Gore Mountain garnet). The garnet is also
used as an abrasive to polish TV and video screens.
After nearly an hour of intense garnet collecting by the students
we settled down to a three hour exercise on one wall of the open
pit designed to determine the genesis of this unique deposit.
This exercise extended the students knowledge of metamorphic
petrology and structural geology and provided them with a much
better appreciation of industrial mineral geology.
The final mine visited on the trip was the NYCO wollastonite
operation near Willsboro, New York. This mine exploits high-grade
metamorphic skarn consisting of wollastonite and garnet. The
open pit was blindingly white on the crisp clear morning we visited.
After examining the rocks the group toured the processing plant
where the students were fascinated by the robotics used for material
processing. Once again, the visit opened the eyes of many students
to the importance, and economic value, of industrial minerals.
The trip back to New York City included a stop at the pre-Revolutionary
War British fort at Crown Point on Lake Ticonderoga where students
examined the classic Ordovician limestone sequence with other
student geology groups from Queens University of Ontario. Finally,
the trip included a stop at Hyde Park, New York on the Hudson
River to visit the home of Franklin D. Roosevelt and the Presidential
museum.
The students produced a field guide for the trip which includes
articles on the geology of the Grenville province of the northeastern
United States and up-to-date descriptions of all the mines visited.
This publication is available for sale from the Society of Economic
Geologists CSM Student Chapter. Proceeds from sale of the book
go toward supporting future field trips for the CSM economic
geology group.
