The mines of Sterling Hill, located in the Borough of Ogdensburg in Sussex County, New Jersey, are among some of the most historical important and mineralogically interesting in the United States.



The mining activities at Sterling Hill relate to an extensive and rich iron and zinc deposits found on site. The ore is unusual, being composed of franklinite (an iron, zinc and manganese oxide), zincite (zinc oxide) and willemite (zinc silicate). Another mineral which played an important role in early to mid 19th century mining on the site was hemimorphite, (a zinc silicate) also know as "calamine" or "maggot ore". The ore deposit at the Sterling Hill is almost unique, the only similar deposit known in the world being located at Franklin, Sussex County, New Jersey, two miles north of this site. A detailed list of the minerals found at Sterling Hill can be found at: http://www.mindat.org/loc-8903.html

Early History

While claims have been made that Dutch immigrants explored, and attempted to mine, at Sterling Hill date as early as the 1640's, no proof of this has yet to be uncovered. The earliest documentary evidence of mining activities on the Sterling Hill site date from 1730, when the property, then known as the "Copper Mine Tract" was divided to the heirs of Anthony Rutgers (deceased) by the Proprietors of New Jersey.

Little is know of the early 18th century mining activities at Sterling Hill. Reports written by Charles T. Jackson, United States Geologist, and A. C. Farrington, mining geologist of the New Jersey Zinc Co. (both reprinted in: New Jersey Zinc Co., 1852) mentions mine workings consisting of shafts and galleries which, based on growth-rings of trees growing in and adjacent to the workings, predated 1739.

In 1769, the property was acquired by William Alexander (the self styled "Lord Stirling") (b. 1724, d. 1783). Lord Stirling undertook the mining of iron on site, sending several tons of ore to his furnace located at Hibernia, New Jersey. Further, he sent several tons of the ore to England for processing, apparently having mistaken the red zincite for cuprite, a red-colored primary ore of copper. It is claimed that his efforts to exploit the deposit failed, mainly because the iron-bearing franklinite was resistant to smelting by period technology.

After "Lord Stirling" drank himself to death during the closing days of the American Revolution, the property was acquired by Robert Ogden of Sussex County. Title of the property eventually devolved to his son, Elias, circa 1795. While the Ogden family was heavily involved in iron mining and iron foundering in the area (owning the profitable Ogden Mine to the south-west of the Sterling Mine, and operating an iron furnace approximately 1 mile northwest of the Sterling Hill) there is presently no evidence that the family ever attempted to exploit the iron deposits at Sterling Hill. However, in an article published in 1822, it was stated that the mine was used by supply zinc for brass during the War of 1812, contemporaneous with the family's ownership, when the United States was largely isolated from European natural resources.

Elias Ogden died in 1805, and his estate was divided among his issue by a commission appointed by the State of New Jersey for that purpose. The ore body was situated upon 3 separate consecutive parcels of land designated as Lots 8, 9, and 10. Each parcel was approximately 46 acres in size. The northernmost parcel, Lot 8, was assigned to Robert Ogden; Lot 9 was assigned to Thomas A. Ogden, and the southernmost parcel, Lot 10, was assigned to Elias Ogden Jr. After this division and until 1897, when the three parcels were consolidated once more under the New Jersey Zinc Co., each lot evolved along separate, albeit parallel, courses.

All three parcels of land were acquired during the period 1818 to 1824 by Samuel Fowler, a physician and amateur mineralogist residing in Franklin, New Jersey. Fowler was also prominent in regional politics, serving in the United States House of Representatives from 1833 to 1837.

Fowler recognized that the mineralogy of the Sterling Hill deposit was significantly different from other iron deposits in the region, and from known zinc deposits, and that many of the minerals occurring in the ore body were new to science. Samples supplied by Fowler to Archibald Bruce, one of the leading American mineralogists, lead to the description in 1818 of the mineral species zincite (previously unknown), the second new mineral described in the Americas and the first major paper of descriptive mineralogy ever published in the United States. He also named the new species franklinite (ostensibly in honor of Benjamin Franklin) and a variety of the mineral rhodonite that is common to the mineral deposit was named in his honor (fowlerite)

More importantly, Fowler's promotion of the ore deposit among geologists, chemists, mineralogists and industrialists throughout the north-eastern United States excited considerable and lasting interest in the potential of Sterling Hill as a nationally-important economic resource.

Fowler, however, experienced considerable problems in exploiting the ores of Sterling Hill on a large scale. The franklinite was extremely resistant to smelting using period iron furnace technology; frequently, the ore would not liberate melted iron but would simply fuse into a solid crystalline mass (called a "salamander" based upon that creature's mythological ability to withstand the effects of flames), necessitating the dismantling of the entire furnace and removal of a several-ton block of worthless material. The franklinite ores were therefor primarily used to augment other iron ores by foundries in New Jersey, New York, and Massachusetts. While it was not clearly understood in the early 19th century exploitation of the deposit, the manganese content of the franklinite helped to reduce impurities in the iron, creating steel of exceptional purity and strength.

It was not until the late 1840's, when further experimentation with the franklinite iron ores, better understanding of iron and steel metallurgy, and considerable improvement in furnace technology resulted in the ability to consistently smelt the ore in quantity, making large-scale exploitation of the deposit economically viable. One of the innovations was replacing charcoal with anthracite coal, providing further impetus to the development of the Pennsylvania coal mining industry.

The resulting metal derived from smelting the franklinite ore was "spiegeleisen", an iron-manganese alloy. The "spiegeleisen" billets were added to iron during steelmaking, and "franklinite steel" became the much-touted product of all of the companies engaged in iron mining at Sterling Hill.

Further, technology was not in place in the early 1800's to smelt the zincite directly into metal cost effectively; the primary product derived from the zincite was "zinc white" (zinc oxide) which formed as a sublimate when the ore was smelted.

Fowler underwrote many projects to develop uses, and therefor markets, for the "zinc white". Principal amoung these was as a replacement for white lead (lead oxide) in commercial paints, which had already been identified as a major health threat to the public. Of nearly equal importance was the fact that zinc oxide based paints, unlike lead based paints, were not subject to "tarnishing by sulphurous exhalations" which had become commonplace in industrialized urban centers. Fowler's Franklin, New Jersey home was painted with the new non-toxic zinc white paint, which was described as of a blue-white or lavender color, as a public demonstration of the product's quality.



However, he ultimately failed in his attempt to profitably operate the mines, and sold off his interests to other concerns.

LOT 8 (The Sterling Hill or New Jersey Zinc Co. Mine)

The mining activities at Lot 8, known as the Sterling Mine or, colloquially, as the New Jersey Zinc Co. mine, primarily concentrated on the open-face mining of zinc and iron during the period 1818 to 1897. Techniques were those traditionally associated with open-face mining, specifically, removal of blocks of ore from a vertical cliff-face using manual and blasting techniques.

Lot 8 was sold by Fowler to Nathaniel Wetherill and William S. Ames in 1836 in conjunction with Lot 9, for a total of $31,247; they transferred their holdings to the Franklin Manufacturing Co. only a month later. The Franklin Manufacturing Co.'s attempts to mine the iron and zinc ores failed, and by 1840 their creditors filed more than $48,000 in unpaid claims against the company with the Sussex County Circuit Court. Their largest creditor, Oakes Ames, a prominent iron founder from Taunton, MA., received the property in satisfaction of a $41,000 loan to the company.

Ames sold the lot to Cyrus Alger in 1845. Cyrus Alger (b. 1781, d. 1856) was a prominent American iron-founder and inventor, of Massachusetts. Trained in iron-foundering by his father, Alger established his own foundry in 1809, at South Boston. Alger's patents included cast-iron cannon, cast-iron plows of malleable iron, and techniques for casting iron in iron molds; he made improvements on reverberatory furnaces and military ordnance.

In 1848, Alger transferred title to the mineral rights of the property to Samuel Fowler Jr., son of original owner Samuel Fowler, who immediately sold the title to the property to the New Jersey Exploring and Mining Co. This corporation had been created in 1848 for the principal purpose of establishing a large-scale mining operation of the zinc and iron deposits at Sterling Hill.

In 1852, after extensive mine development on Lot 8 and the erection of an extensive extractive facility and paint factory in Newark, New Jersey, the New Jersey Exploring and Mine Co. changed its named to the New Jersey Zinc Co. In their first annual report, the company stated that their capital was $1.2 million.

In that year, the company was producing large quantities of paint based on zinc white, and were also manufacturing an orange paint out of finely ground zincite and a brown paint made from finely ground franklinite. Their annual report contained a report from a special committee of the New York Board of Assistant Alderman espousing the universal replacement of lead-based paints with zinc paints, as well as testimonials from the United States Navy Yard at Gosport, Virginia, on the durability of zinc paint as a marine anti-fouling coating.

One of the early members of the firm was Samuel Wetherill, (b. 1821, d. 1890) who rose to prominence as one of the foremost inventors of extractive metallurgical processes of the mid to late 19th century. Wetherill perfected a new process used to directly extract zinc white from the Sterling Hill ores in a manner more cost effective than any tried previously. He also patented processes for the production of zinc metal and rolled sheet zinc.

In 1880, the New Jersey Zinc Co. was absorbed by the New Jersey Zinc and Iron Co. In 1897, the New Jersey Zinc and Iron Co. was amalgamated with neighboring mining operations at Sterling Hill to form the New Jersey Zinc Co.

Lot 9 (The Passaic Mine)

The mining activities at Lot 9, (known as the Passaic Mine) primarily concentrated on the open-pit mining of zinc and iron during the period 1824 to 1897. Techniques were those traditionally associated with open-pit mining, specifically, the excavation and removal of blocks of ore from a man-made depression in the earth using manual and blasting techniques.

Fowler sold Lot 9, later known as the Passaic Mine, to Nathaniel Wetherill Jr. and William S. Ames in 1836. A month later, they transferred their titles to the Franklin Manufacturing Co. which, by 1840, was bankrupted and its assets liquidated to satisfy numerous creditors. The property was given to Samuel Fowler Jr., who, in 1850, sold the mineral rights to the Consolidated Exploring and Mining Co.

The Consolidated Exploring and Mining Co. liquidated their holdings in 1853, selling Lot 9 to the Passaic Mining and Manufacturing Co.

The company changed its named in 1871 to the Passaic Zinc Co., and continued in operation on the site until 1897, when the company merged with adjacent owners to form the New Jersey Zinc Co.

By 1871, the milling activity at the Passaic Mine appears to have been divided into two distinct operations. The franklinite-zincite ores were sent to the Passaic Mill on site, while the hemimorphite excavated in the "calamine mine" (an open-pit excavation into soft, unconsolidated ground located between the East and West veins) were sent to a separate on-site mill specifically designed to handle that ore.

THE PASSAIC MILL:

The Passaic mill for the beneficiation of the zincite-franklinite based ores was constructed on site in 1861. An 1871 description of the mill stated: "These works are a marvel of mechanical ingenuity. As the uninitiated one goes into the large building he sees nothing but a whirl of intricate machinery and streams of splashing water; he hears nothing but the crunching noise of ore being crushed and the roar of ponderous wheels, shafts, rollers and other mechanical apparatus...

"Preliminarily, the ore was broken in pieces approximately four inches in diameter, and passed through two sets of crushing rollers. The crushed ore was passed via an Archimedes screw to a set of revolving screens for classification by size. Ore that passed through the first screen, which had 8 holes to the inch, were passed on to the second screen which had 30 holes to the inch. Ore too coarse to pass through the first screen was returned to a second set of crushing rollers via another Archimedes screw, and re-screened.

Ore passing through the first screen, but too coarse to pass through the second, finer screen, was "conveyed in spouts" to jigs, where "... by means of a cam motion the ore is separated from the limestone; the ore going through the bottom of the jigs into large tanks, while the limestone flows over the top and is elevated with water to the top of the building; from here the water carries the limestone down a spout three hundred feet in length and deposits it in a meadow below... "

"These jigs were invented by and patented by the Passaic Zinc Co. There are two of these jigs in operation now, separating 400 tons of ore per month. A large amount of water being required for this operation and method of separation, is supplied by a huge plunger pump, which forces the water into a large tank on the top of the mill building, so as to give it a pressure back through the different pipes...

"The fine ore which passes through the fine screen, is conveyed to a revolving table of circular form, over which flows a stream of water.

"As much of the red ore pulverizes very fine, it would be carried away with the limestone but for the revolving table separation. As the table revolves the zinc, being heavier than the limestone, falls to the bottom, and leaves the fine limestone to be carried away by a stream of water flowing over the table, while the pure ore is taken off by a stream of water from a jet pipe.

"By this ingenious mass of machinery the ore requires no handling from the time it is put into the rolls until it comes out separated." [In: Anon. Herald and Democrat (Newton, NJ)27 July 1871

The concentrated ore was carted overland to the Ogden mine, about two miles south-east of Sterling Hill, then transported by railroad to Nolan's Point, on Lake Hopatcong, and shipped by water to the Passaic Zinc Company's Jersey City manufactory for production of zinc white (Herald and Democrat, 27 July 1871).

The mill was abandoned in 1877, when more efficient transportation (the New Jersey Midland Railroad) became available and enabled the Passaic Zinc Company to transport unconcentrated ores cost-effectively to their Jersey City, New Jersey facility for beneficiation.

While no detailed description of the mining methods used to recover the hemimorphite at the "Calamine Mine" has been found, it is probable that extensive technology was not be required for the actual mining of the hemimorphite and that simple digging sufficed.

Hoisting of ore was accomplished using a portable hoist engine which raised ore on an inclined plane. No trace of the inclined plane is apparent today; it is possible that the structure was mined away by the New Jersey Zinc Company during the 20th C to provide fill for backfilling stopes in underground operations.

The excavated ore was transported a short distance yo the "Calamine Mill" which had been constructed in the summer of 1871 for the sole purpose of beneficiation of the hemimorphite ore. Details of the circuit used in treating the hemimorphite are sketchy; in general terms, it appears that after mining, the hemimorphite ore was crushed, washed, and dried for shipment.

One source, published soon after the mill opened, merely states that it consisted of an "engine, screen and jigs" to provide "five different grades of ore". How the various grades or ore differed from one another is uncertain.

A description of the mill in 1883 provides greater detail on the equipment in use, but does not provide any detailed information on the sequence of the treatment process itself. The mill was fitted with a 6 horse-power Hoadley engine which operated stamps for the crushing of the ore, washers for washing the ore, and operation of a No. 3 Knowles pump, which had a 10-inch diameter cylinder with a 16-inch stroke. The Knowles pump was probably used to elevate water to a holding tank for use in washing operations. [Darton, Nelson, Scientific American Supplement Vol. 16 p. 6278 (1883)]

Following washing, the hemimorphite was "dried in heaps and shipped" either to the Passaic Zinc Co.'s plant or to buyers elsewhere. Mention is made that one primary client for the hemimorphite was "a Bethlehem company", probably the Lehigh Zinc Company, who used the ore in the manufacture of strip zinc

A description of the Passaic Zinc Co.'s mining activities at the Passaic Pit in 1883 was published by N. H. Darton:

"The principal mine is in the main [east] vein, from which 50 tons per day are taken, and the basin where the silicate or calamine [hemimorphite] is taken out. A large engine house is erected nearly over the mouth of the main vein, which has a shaft 240 feet in depth and works two drills. Two forty horse power boilers are in the engine house, working an 8 inch mining pump with 5 foot stroke, an air compressor, a No. 5 Blake pump in the level, and a No. 1 Worthington double action pump in the bottom of the shaft, besides some smaller machinery in the shop, the hoisting engine, etc.

"At the calamine mine a few hundred yards away a small portable hoisting engine is used, and at the mills for washing it at the bottom of the hill, a six horse power Hoadly engine for running the stamps, washers, and a No. 3 Knowles pump, 10 inch cylinder, 16 inch stroke. The washed silicate is dried in heaps and shipped direct to their works, or in some instances sold to other companies."

At the time of Darton's writing, 60 men were engaged in mining activities the Passaic Mine.

Lot 10 (The Noble Mine)

The mining activities at Lot 10, (known as the Noble Mine) primarily concentrated on the open-pit mining of zinc and iron during the period 1847 to 1897. Techniques were those traditionally associated with open-pit mining, specifically, the excavation and removal of blocks of ore from a man-made depression in the earth using manual and blasting techniques.

The history of Lot 10 is somewhat more complex than that of the other two parcels comprising Sterling Hill. The complexity arises from the fact that the rights to the iron and zinc ores were severed early in the parcel's history, with contemporaneous and competing companies attempting to exploit the same ore.

After the death of Samuel Fowler in 1844, Lot 10 was inherited by his daughter, Mary Estelle Fowler, and, in 1847, was acquired by her brother, Samuel Fowler Jr. He sold the property to the New Jersey Zinc and Copper Mining and Manufacturing Co. that same year, who remained in possession of the parcel until 1853, when Fowler repurchased the lot.

Inexplicably, Samuel Fowler Jr. severed the zinc and iron mineral titles, selling the zinc title to the National Paint Co. They subleased mining rights on the parcel to the Consolidated Franklinite Co. beginning in 1859, Their attempts to economically exploit the deposit failed, and the National Paint Co. went into bankruptcy prior to 1861; to further complicate the title history, title to the parcel was bestowed on separate groups by the Peter S. Decker, Sheriff of Sussex County, at a court-ordered public auction, and by George W. Savage, Receiver of the State of New Jersey.

Decker transferred title to the parcel to Ashley Ball in 1861, who operated the site for two years before selling his holdings to John P. Harley in 1863. Harley was bought out in 1864 by George W. Jewitt, William C. Squier, and Henry Aitkin, a compendium of businessmen who maintained ownership of the zinc title until 1896. In that year, their holdings were acquired by the Passaic Zinc Co. and merged into the New Jersey Zinc Co. in 1897.

However, Savage, acting as receiver of the State of New Jersey, transferred title to the zinc ores on the property to John Silsby in 1878 at the time of the final liquidation of the National Paint Co.'s assets. Silsby had previously sublet a mining lease on Lot 10 from the Franklinite Steel and Zinc Co., and was actively engaged in iron mining on the site. The Franklinite Steel and Zinc Co. compounded matters further by leasing the same rights to Charles W. Trotter of Brooklyn, N.Y. simultaneous with Silsby's lease. This confusion continued until 1882, when Silsby sold his interests in the parcel to the Manganese Iron Ore Co.

The history of the iron title to the parcel is less convoluted. Samuel Fowler Jr. transferred the iron title to Samuel Brooks and Silas Stillwell in 1852. They conveyed the property to the Sussex Iron Co. in 1853, who, in turn, sold the parcel to Samuel Fowler Jr. and James L. Curtis in 1854. In 1855, the parcel was conveyed to the Franklinite Steel Co., of which Curtis was President.



The Franklinite Steel Co. was merged with other interests in 1871 to form the Franklinite Steel and Zinc Co., with Curtis serving first as Vice President, then President of the corporation.

In 1878, the parcel was transferred to the Manganese Iron Ore Co., John Silsby, President, which had previously acquired title to the zinc on the parcel. In 1882 the company became bankrupt and its assets liquidated. The parcel was acquired in 1887 by Edward Cooper and Abram S. Hewitt. With their acquisition of the Manganese Iron Ore Co. holdings, Cooper and Hewitt also received part of the conflicted zinc title, the other part then claimed by Jewitt, Squier and Aitkin.

Edward Cooper (b. 1824, d. 1905) was a prominent American manufacturer and civic leader, of New York City. Cooper organized the company of Cooper, Hewitt & Co., a nationally-prominent 19th century iron and steel manufactory and pioneer producer of iron girders and beams.. Cooper invented several innovative devices for improvements of iron manufacture, including the regenerative hot-blast stove for blast furnaces. Cooper was also one of the primary forces behind the destruction of the "Tweed Ring" in New York City, agitating for political reform; in 1879, he was elected Mayor of the City of New York on a Republican-Democrat fusion ticket. He was president of the Board of Trustees of the Cooper Union in NYC, founded by his father.

Abram Stevens Hewitt (b.1822, d. 1903) was also a prominent American manufacturer and civic leader, of New York City and Ringwood, New Jersey. Hewitt joined with Edward Cooper to form the company Cooper, Hewitt and Co., a nationally-prominent iron and steel manufactory and pioneer producer of iron girders and beams. Hewitt was responsible for erecting the first open-hearth furnace in the United States for steel production. He was elected to Congress in 1874, and in 1876 served as the chairman of the Democratic National Committee during the Hayes-Tilden campaign. He served on the committee that established the Electoral Commission that evolved from the campaign. Hewitt was a major motive force behind the effort to break the "Tweed Ring" in New York City, and in 1886 was elected Mayor of the City of New York.

Amoung his many projects in office was the establishment of the Rapid Transit Railroad in New York City. He was a trustee of Columbia University, Barnard College, and the Carnegie Institute, as well as President of the American Institute of Mining Engineers.

In 1896, the two groups consisting of Cooper and Hewitt, and Jewitt, Squier and Aitkin sold their holdings to the Passaic Zinc Co., which merged into the New Jersey Zinc Co. in 1897.

Consolidation

In 1897, the New Jersey Zinc and Iron Co., along with the Passaic Zinc Co. of Lot 9 (the Passaic Mine) and the sundry owners of the Noble Mine on Lot 10 (Cooper and Hewitt; and Jewitt, Squier, and Aitkin) amalgamated to form a new corporation, consolidating all of the mineral properties at Sterling Hill. This new company, the New Jersey Zinc Co., undertook an ambitious program of mine development on site; above ground workings were abandoned and efforts concentrated on underground mine development using the most modern technologies then available.

The Board of Directors of the new company consisted of August Heckscher, David B. Jones, Stephen S. Palmer, Moses Taylor Pyne, John L. Riker, Charles B. Squier, and Samuel Price Wetherill.

The new mining operations at Sterling Hill officially began producing ore in 1912. By 1916, a mill was constructed on site to begin grinding and beneficiating the ore on site before it was sent, via railroad, to the company's Palmerton, PA refinery.

Among the most prominent consultants to the new venture was Thomas Alva Edison (b. 1847 d. 1931), a prominent American inventor. Edison had acquired an iron mine several miles from the Sterling Hill mines and had developed several innovative techniques and processes for beneficiating the ores and smelting metal. He maintained an active correspondence with the officers and management of the New Jersey Zinc Co., offering detailed advice on process technology, as well as designing equipment for the the company.

The underground workings at Sterling Hill created by the New Jersey Zinc Co. were on a large scale. Shafts and tunnels to maximize access to the ore deposit were established, and by 1922 tunnel complexes existed at the 180, 340, 430, 500, 600, 700, 800, 900, 1000,1100, 1200, 1300, 1400, 1500, 1600, and 1680 foot levels. The tunnel complexes were roughly elliptical in shape. By the 1960's, levels at the 1750, 1850, 1950, 2050, 2150, 2250, 2350, 2450, and 2550 foot levels were operational.

The principal mining method in use was the shrinkage or back stope method. From each level, stopes 20 feet wide were opened perpendicular to the strike of the orebody; stopes were separated by approximately 40 feet, leaving a pillar 20 feet wide between each stope. Upon completion of all ore removal, the stope was backfilled with rock quarried on site from the Fill Quarry. Upon completion of the stopes, the pillars were also mined, using a variation of the top-slice system.

The mined ores were brought to the surface in a 2.7 ton skip. Based on extant mine flow charts dating from 1933, the treatment of the ores on site was as follows: The ore was passed through a washing trommel with 2-inch openings; material too large to pass through the openings was passed to a picking table where ore masses were separated from scrap steel and wood waste, then passed through a gyratory crusher. The coarsely crushed ore was then passed through a Niagara vibrating screen with 1.25-inch opening, and the passed ore placed in 300-ton capacity crude ore storage tanks. From the crude ore storage tanks, ore was carried by belt conveyors to the Fine Crushing department, where it was passed through a #2 roughing screen with 0.750-inch openings; oversized ore fragments were recrushed and run through the cycle until conforming to size. The ore which passed through the roughing screens was passed through a #1 Rowand tower screen with 0.0880-inch openings. The ore was then passed through two dust separators, and the passed ore was transmitted to the Sizing department. Dust was sent to the Fines department, where it was bagged and transmitted to New Jersey Zinc Co.'s Palmerton, PA., facility for treatment and metal recovery. Ore from the Fine Crushing department, crushed to a size of 0.0880-inch or less, was take to the Sizing department where it was run through a series of nine different sized Rowand tower screens with openings varying from 0.0820 to 0.0130-inch. Each of the nine different size fractions were run through a magnetic separator, which separated franklinite (magnetic) from willemite and zincite (non-magnetic). The franklinite fraction was transmitted directly to the company's Palmerton, PA., facility for further treatment. The non-magnetic fraction was transmitted to the Jigging department, where the crushed ore was treated with Hutch jigs. Jig tailings were dewatered and returned underground to be used in back-fill operations in the mine; jig middlings were transmitted to the Tabling department for further beneficiation; and the primary jig yield of willemite/zincite was dewatered, dried, and sent to Palmerton, PA., for further treatment. Middlings sent to the Tabling department were first deslimed to remove fine dusts, then run through Pocket Pellett classifiers. The classified ore was tabled using twenty Wilfley tables; table tailings were dewatered and returned underground for back-filling, table middlings were recycled through the tabling process, and the primary table yield was dewatered, dried and transmitted to Palmerton, PA.

At Palmerton, PA., the specific ore fractions (franklinite or willemite/zincite) were treated by traditional pyrometallurgical techniques (roasting) to yield either zinc spelter (impure zinc metal) or directly oxidized into zinc oxide and recovered by precipitation as a powder, based on production needs and ore-feed characteristics.

In the early 20th Century, the New Jersey Zinc Co. provided valuable social services to the miners living in the Ogdensburg area, including a well-appointed company hospital, clubrooms for the miners and their families, bowling alleys, tennis courts, swimming pools, and even a summer camp for the miners' children (Camp Riker at Lake Hopewell, New Jersey). The mining company even provided company-subsidized housing for employees (consisting of 4-room bungalows for laborers at $8 per month in 1922, and "comfortable houses" for staff at $17 a month).

By 1940, the New Jersey Zinc Company was producing a wide variety of products in addition to spiegeleisen. These included slab zinc (cast zinc ingot) for applications in galvanizing of sheet iron, for alloying into brass and die casting alloys (such as the New Jersey Zinc Co.'s proprietary zinc alloy Zamak); rolled zinc, consisting of sheet zinc used for dry cell batteries, weathering stripping, boiler plates, fencing, and as roofing material (one form being a corrugated zinc roofing sheet given the proprietary name of Zilloy, which, being iron-free, was not subject to rusting); zinc oxide pigments for paints, rubber, ceramics, linoleum, plastics, and printing inks; zinc oxide of pharmaceutical grade, used in ointments, dental cements, and cosmetics; zinc-based luminescent paints (which replaced highly toxic radium-based compounds) for watch dials, paints, and plastics; zinc sulphide pigments for paints, vitreous enamels, ceramics, and plastics; and zinc borate for fire retardant textiles. These products were marketed under the name of Horse Head Products, derived from the New Jersey Zinc Co.'s corporate logo.

In addition to the Ogdensburg, New Jersey mining operations, New Jersey Zinc Co. also operated mines in Franklin, Sussex County, New Jersey (two miles due north of Sterling Hill; at Friedensville, PA., Austinsville, VA., Gilman, CO., amd Hanover, NM.

In 1948, when the New Jersey Zinc Co. celebrated their 100th anniversary (based not so much upon the corporation's date of founding as the date of the oldest corporate entity ultimately absorbed into New Jersey Zinc), the President of the company was Henry Hardenbergh, Marshall L. Havey serving as Executive Vice President, Walter R. Anyan as Secretary, and Samuel Riker Jr. as Treasurer.

The New Jersey Zinc Co. abandoned the site in 1986, after attempts to reduce property tax assessments on the Sterling Hill site were unsuccessful.

In 1989, the property was acquired by Richard Hauck and Robert Hauck, of Bloomfield, New Jersey, who have converted the facility into a museum dedicated to the history of mining at Sterling Hill, general mining history, and the mineralogy of the Sterling Hill orebody.