CHRONICLES OF
CENTRAL PENNSYLVANIA MINERALOGY
Part One
Jay L. Lininger
Dillsburg, PA
Webmaster's Note: The following six part
article was originally written by the late Jay Lininger for the Central Pennsylvania Rock & Mineral
Club and published in ROCK BUSTER NEWS, an award winning
newsletter. Jay
Lininger was well known in Pennsylvania mineralogical circles. He was co-founder
and publisher of MATRIX - A Journal of the History of Minerals,
now available for purchase at Penn Minerals.
WHY DID THEY CALL IT MOORE’S MILL?
Many of you reading this article have visited or are at least familiar
with the location we call Moore's Mill. The location, which has produced some of the
finest phosphate minerals found in Pennsylvania, is located about four miles west of the
village of Mt. Holly Springs in Cumberland County. My fascination with the location
began in 1962, when as a young collector I struggled to find it for the first time. In
"those days" there was no popular field collecting guide such as the Geological
Survey Publication G33. Using my treasured and well-worn copy of Samuel Gordon's
"Mineralogy of Pennsylvania" (1922), I spent hours hiking out on the northern
rim of the South Mountain searching for what turned out to be a small water filled pit
that was incidentally, not covered with bags full of collectable minerals. Just what was
this, one of a kind mining operation that lay hidden in the woods outside of Mt. Holly?
Over the years, I've been able to fill in some of the pieces.
THE LOCATION HAS A HUNDRED YEAR HISTORY
The South Mountain of the nineteenth century was an area which bustled
with activity. The iron mining industry in the Commonwealth was in full production during
that era. Coupled with the development of the coal fields to the north and west, the two
commodities had propelled Pennsylvania into the industrial giant among the states. The
South Mountain had produced its share of successful iron manufacturing operations with
several dating back to the earliest days of the American Revolution. Several notable
operations included the Pine Grove-Laurel Bank area (Cumberland County), the Mont Alto
complex (Franklin County), and the Catoctin operation in northern Maryland. As active
prospecting took place in all areas of the South Mountain, a number of large and valuable
white clay deposits were located, particularly in the Mt. Holly Springs area. The
geological forces which deposited the large residual beds of iron ore, had also deposited
large beds of pure white clay. A new industry thus developed at Mt. Holly Springs in the
era following the Civil War. The clay was well suited to the manufacture of tile and
brick, and was found to be an excellent whitening agent in the manufacture of paper.
Sometime during the latter part of the 1880's, (no actual date has been recorded), the
deposit of clay near Moore's Mill was located. The clay at this location was as pure as
the deposits on the other side of the mountain, but had one peculiar characteristic. It
was contaminated by numerous large pods of a hard clay that was later discovered to be
pure aluminum phosphate - wavellite. The discovery of this curious deposit in an area
known as the Stuart tract, prevented its exploitation as a clay mine for several years.
History doesn't record who recognized the potential that existed in the
bed of phosphate nodules, but someone connected the value of the ore with the newly
developing industry in the manufacture of safety matches. The flammability of pure
phosphorous was known for many years, but had no practical use until the invention of the
safety match in 1855. This handy little device consisted of a wooden matchstick with a
phosphorous coating on the tip. The phosphorous was covered with an air tight coating
which could be removed by striking the match tip on a coarse surface, thus igniting the
phosphorous. Up to this point all phosphorous used in safety match manufacture was
processed from animal bones or organic rock phosphate deposits. The bone or rock phosphate
was crushed, roasted and treated with sulfuric acid to produce the refined product. Now
confronted with an available source of high grade ore, a new reduction process would be
required.
In 1898 a group of Philadelphia businessmen formed a new venture which
they named the American Phosphorus Company. Aware that they would need to develop a new
ore reduction process, they hired G.C. Landis, a well known chemist to supervise the
effort. The company began construction of a processing plant and moved to acquire the ore
deposit. The land which contained the phosphate bearing clay was owned by T.J. Spangler of
Mt. Holly Springs. Spangler was convinced that the deposit had great value, and instead of
selling the land, devised an arrangement in which he would be superintendent of the mine,
and would be paid by a royalty on each ton of ore extracted. He of course would be in a
good position to monitor how much ore was extracted.
The mine was opened in 1900, but several non-productive years were spent
in prospecting the deposit and the experimentation in reducing the ore. G.C. Landis was
familiar with the patents available in phosphorous reduction, and drawing on this
knowledge devised a method to smelt the wavellite in a satisfactory manner. The process
required the introduction of great heat, and could only be attained by the use of the
newly invented electric furnace. By 1905 all aspects of the mining and ore processing were
in full operation. The ore was extracted by pick and shovel and hauled down the mountain
to the mill which was situated near the bank of the Yellow Breeches Creek. About 400 tons
of ore was mined in 1905, but the open pit, now about 30 feet deep, began to experience
severe water problems. Later in the year a test shaft was sunk near the open pit. At the
12 foot level, a large clay mass was encountered, which proved to be 40 feet thick. At the
base of clay, the miners struck 16 feet of manganese ore.
In spite of the early successes, signs of economic trouble were on the
horizon. The processed phosphorous was a dangerous commodity, and some apparent
mishandling led to a disastrous fire in the fall of 1905. This was a setback that caused a
disruption in the processing of ore, but the company management raised the necessary
capital to rebuild the plant. Water continued to plague the mining of ore, and its removal
increased the cost of recovery. Several months after the rebuilt processing plant went
back into operation, the management of the company recognized that the cost of operation
for the electric reduction was greater than the value of the phosphorous it produced. In a
desperate move to regain some semblance of profitability, the company owners decided to
move the processing plant to York Haven, which was located by the Susquehanna River. In so
doing, the company could obtain more cost effective (river turbine) electricity for
running the furnace. The move was successfully completed by the early part of 1906.
During the summer of 1906 the mine was visited and described by George
W. Stose, the eminent Appalachian geologist who was working for the U.S. Geological
Survey. During his visit the mine was filled with water, but the miners were building a
drainage channel to carry excess water downhill. This engineering solution helped keep the
mine in workable condition for several more years. In spite of attaining maximum
efficiency, the American Phosphorous Company was unable to earn the profit it needed to
survive and was closed by the end of the decade. Once again, a well conceived American
enterprise failed because technological problems could not be overcome.
The mine had been closed for a number of years when it was visited by
Pennsylvania's pre-eminent mineralogist Samuel G. Gordon in 1919. Although existence of
the location was mentioned in a publication by mineralogist John Eyerman (1911), Gordon
was likely to have been the first mineralogist of note to visit the occurrence. The
Cumberland County of 1919 was a sparsely populated agricultural county, and thus Gordon,
when preparing his field notes, placed the mine near the closest location of note: Moore's
Mill. This was a reasonable assumption for the time, because the numerous grain grinding
mills along the Yellow Breeches Creek were important landmarks in the community. When
Gordon published his findings in the Proceedings of the Academy of Natural Science in
Philadelphia later that year, he forever enshrined the name of Moore's Mill in the
mineralogical literature.
Gordon later analyzed the abundance of species collected on that field
trip and confirmed the presence of five distinct phosphates: wavellite, cacoxenite,
beraunite, variscite and strengite. The variscite and strengite were new species to
Pennsylvania.
RECENT HISTORY
Little attention was paid to the location until 1965 when Davis Lapham
and Allen Geyer published the first of the three popular editions of G33, "Mineral
Collecting in Pennsylvania." Soon mineral collectors were able to easily locate the
obscure location. As a young collector, I was fortunate in being able to collect each of
the species described by Gordon, even though several were rare. One of them was a
blue-green massive mineral which was found intergrown with wavellite in the hard nodules.
I presumed this mineral to be variscite. And why not? Wasn't variscite a bluish-green
mineral? More experienced collectors were auspicious however, including early CPR&M
club member Dorothy Herman. Dottie was an astute and knowledgeable field collector, and
the massive blue mineral made her curious enough to take it to state mineralogist Davis
Lapham for investigation. His subsequent analysis determined the species to be turquoise.
Dottie Herman's effort produced a species new to the Pennsylvania list in 1965. The true
variscite at Moore's Mill occurred in clear to pale violet radial crystal clusters and
botryoidal masses.
Increased collecting of the area was conducted by a new generation of
Pennsylvania collectors in the 1970s. The group, unofficially headed by Martin Anne of
Wrightsville, decided to excavate in an area north of the pit which they presumed to be
the ore loading zone. Their efforts were rewarded with the discovery of numerous large
superb specimens of cacoxenite and beraunite. A photograph of one of these specimens was
featured on the cover of the special Pennsylvania issue of ROCKS AND MINERALS magazine
(May-June 1978).
This story provided a brief overview of the hundred year history of
Pennsylvania's most unusual phosphate occurrence. Do other undiscovered phosphates still
exist at Moore's Mill? It is likely that they do, and perhaps another chapter in the story
of this unique Central Pennsylvania mineral location is waiting to be written in the
future.
Stay Tuned for Part Two! "The Copper
District of Adam's County"
