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Franklin orebody
Overview
The Franklin orebody was the larger of the two Zn-Mn-Fe deposits in
the region, and was economically mined-out in September 1954. There is
no access to the flooded underground workings today.
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Longitudinal elevation of the Franklin ore
body, projected on an arbitrary north-south vertical plane. Coordinates
are in feet using a New Jersey Zinc Company coordinate system (see
Dunn, 1995, for explanation). After Frondel and Baum
(1974).
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Detailed geologic maps for a small portion of the Franklin orebody
are preserved in the Franklin Mineral Museum; a number of these formed
the source for those published in Frondel and Baum (1974).
The internal structure of the Franklin Zn-Mn-Fe orebody is quite
complex. The deposit consists of interlayered lens-like beds of zinc ore
minerals, mixed with varying amounts of calcite, and lens-like beds of
calcsilicate rock. Fractures and faults were common in both the Franklin
and Sterling Hill deposits, and a great variety of late-stage
hydrothermal minerals were found. The south end of the east limb at
Franklin may have been an overturned isoclinal fold; it was roughly
twice the thickness of the west limb.
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Vertical section of the Franklin ore body,
showing deformed structure in the keel area. Key: calcsilicate
bodies, black; A = franklinite, willemite, calcite, locally with
zincite; B = franklinite, willemite, zincite, locally without
zincite; H = calcite, franklinite, willemite; K = massive
franklinite with sparse calcite; L = massive calcite; M = calcite
with sparse franklinite; P = intrusive pegmatite body (?). Coordinates
are in feet using a New Jersey Zinc Company coordinate system (see
Dunn, 1995, for explanation). After Frondel and Baum
(1974).
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