|
Black
Hills Pegmatites!!
By Thomas A.
Loomis TESTING
from MATRIX Vol. 10, No. 3 Issue
For the pegmatite collector, the Black Hills may be
paradise. Within its borders, thousands of pegmatites occur. In fact, pegmatite
dikes crisscross Mount Rushmore. Cleophas C. O’Harra (1902) called this the
“Mineral Wealth of the Black Hills”. United States Geological Survey
geologists mapped individual quadrangles and reported on mined pegmatites by the
thousands in the 1940’s. Up to 390 mineral species (Farrar, 2002) are found in
the Black Hills, 22 of these are new to science. Most of the new minerals are
phosphates and are found in pegmatites. The prolific Tip Top mine accounts for a
majority of these and are discussed in the accompanied article. The remainder
along with other important pegmatite localities and their history are discussed
here.
The Helen Beryl mine near Custer, SD
The Black Hills proper includes an area of approximately
1,600 square miles. Central to the Black Hills is Harney Peak, the highest point
at 7,242 feet above sea level. Harney peak is comprised of 1.7 billion year old
granite and crops out in a roughly circular area of no more than 10 miles in
diameter. Flanking the granite are 2.5 billion year old metamorphic rocks in
which most of the pegmatites have intruded. The pegmatites occur within an area
of about 275 square miles around Harney Peak.
 \
Harney Peak - highest point in the Black
Hills.
The pegmatites range from a few inches to more than a mile
in length and up to 500 feet wide. Rocks within the pegmatites are primarily
plagioclase feldspars (oligoclase and albite), potash feldspars (perthite and
microcline), and quartz. Spodumene, lepidolite, muscovite, and tourmaline are
major constituents in a few pegmatites (Page, 1953 & DeWitt, 1986). In
general, only about one percent of the pegmatites are compositionally zoned and
are considered complex according to Norton (1962). Black Hills pegmatites are
not known to contain cavities and have not produced any gem crystals of
significance. Pegmatites are generally grouped within three major mining
districts, which are the Keystone, Custer, and Hill City districts in the
southern Hills, and the Tintic district in the northern Hills. Only the Keystone
and Custer districts will be emphasized in this article. In particular, the
Barker, the Big Chief, Hugo, Ingersoll, and the Tin Mountain pegmatites will be
highlighted.
The McMackin mine (also known as the Crown mine) was the
first pegmatite to be mined in the Black Hills for mica in 1879.
This was followed by the discovery of several other pegmatites in the
area through 1884 and is recognized as the first period of pegmatite mining in
the Black Hills. Records indicate approximately 8,000 pounds of mica was
produced during these early days of mining. The next period of pegmatite mining
is marked when tin was discovered at the Etta mine in 1883. Tin mining lasted
through 1893, when the Harney Peak Tin Company collapsed through scandal and
practically nonexistent production. Ironically, the Black Hills would ultimately
capitalize on the situation through the discovery of many viable economic
minerals from pegmatites originally mined for tin. Through it all, countless
pegmatites were discovered and lithium ore would define the next wave of
pegmatite mining. This wave,
however, would gain not collapse under false pretense, but would grow with
economic vitality. The Black Hills would then become a powerhouse of mineral
resource and lead the nation in the production of lithium, beryllium, mica,
feldspar and many other ores.
In 1898 the Rheinbold and Company began spodumene mining at
the Etta mine, which became the largest single source of spodumene in the Black
Hills. Spodumene was mined for its lithium content and before long several other
mines began operations with discovery of amblygonite, lepidolite, and triphylite
as alternative sources of lithium. As lithium production drove economic
viability at the pegmatites other minerals were discovered and mined as
byproducts. These included beryl, columbite-tantalite and caesium. Westinghouse
Electric and Manufacturing Company entered the Hills when electrical and other
applications required the insulating qualities of mica. This event resulted in
the production of mica up to 1.5 million pounds annually during the period of
1906 to 1911. Yet another boom resulted when freight rates dropped in 1923 and
the vast deposits of feldspar were mined Keystone Feldspar and Chemical Company.
Cross-Section of the Etta pegmatite.
Rendered by G.M. Schwartz and reproduced from Economic Geology, vol. 20 (1925)
The Etta mine in 2001. Photo by Tom Loomis.
William Blake postulated the first explanation of zoning in
pegmatites in the Black Hills pegmatites as early as 1883. But it was Kenneth
Landes who first studied the Black Hills pegmatites in detailed attempt to
classify and explain their origin in 1928 and 1933. During the1940’s a group
of USGS geologists invaded the Black Hills as part of its Strategic Mineral
Investigations towards the war effort of quantifying viable mineral reserves.
Subsequent investigations followed with detailed studies completed by USGS
geologists in part for the U. S. Atomic Energy Commission. One of these studies
“Geology of the Hugo Pegmatite, Keystone, South Dakota” provided a very
detailed look at zoned pegmatites and disputed Landes’ theories on origin.
Samuel Scott in 1897 wrote the first book on descriptive
mineralogy of the Black Hills. Titled “Rocks, Minerals, and other Resources of
the Golden Black Hills of South Dakota and Wyoming”, this short description of
Black Hills minerals bestowed the first look at pegmatite minerals in the Hills.
This work is today highly sought after as a Black Hills mining relic. Victor
Ziegler in 1914 published his work “The Minerals of the Black Hills”. This
was the first comprehensive publication on Black Hills mineralogy and also
provided insight to the origin of pegmatites. Instrumental to the study of Black
Hills mineralogy was Willard (“Bill”) L. Roberts. Roberts along with George
Rapp in 1965 updated Ziegler’s work with hundreds of new mineral localities in
“Mineralogy of the Black Hills”. Paul
Moore from the University of Chicago with Bill Roberts in the 1960’s studied
phosphate mineralogy of the pegmatites. Their work resulted in the discovery of
three species new to mineralogy. Moore’s work culminated in a fine article
titled “Pegmatite Phosphates: Descriptive Mineralogy and Crystal Chemistry”
and was published in a 1973 issue of the Mineralogical Record. Through the
following years several papers were written on new discoveries in the Black
Hills and published in the American, Canadian, and British mineralogy
periodicals.
Some of the
most important locality indexes of the Black Hills include:
- Bureau
of Mines staff (1953) Black Hills Mineral Atlas parts 1 & 2.
- Tullis
(1952) Beryl Resources of the Black Hills.
- Roberts
and Rapp (1965) Mineralogy of the Black Hills. This includes a very
complete mine index as an appendix.
- Smith,
A. E. and Fritzsch, E. (2000) South Dakota Mineral Index
“Type
Locality Minerals of the Black Hills, South Dakota” by Triscori and Campbell
(1986) provides a good summary of significant discoveries of pegmatitic minerals
found in the Hills. Aside from the beryllophosphate minerals from the Tip Top
mine, other rare minerals such as cern?ite, olmsteadite, perloffite,
sinkankasite and walentaite were first discovered from Black Hills’ pegmatites
and are briefly discussed in this article. Other noteworthy occurrences in the
Black Hills also include:
Olmsteadite - Big Chief mine. Crystals to 1.1cm in Siderite.
Probably the finest Olmsteadite in existence.
Museum of Geology specimen and Former Bill Roberts specimen.
Tom Loomis photo
- The
second world occurrence of scorzalite found at the Victory pegmatite near
Custer (Pecora and Fahey, 1949).
- The
first occurrence of montgomeryite in a pegmatite was discovered at the Etta
mine (Moore, 1964).
- The
first occurrence of scorodite in a pegmatite reported from the Etta mine (Zodac, 1953).
- The
first occurrence of wodginite in the United States was found at the Peerless
mine (Cern? 1985).
The Black Hills can also boast the largest
spodumene crystals in the world occurring up to 50 feet in length and weighing
more than 90 tons!
Sinkankasite sprays to 1mm. Tom
Loomis collection and photo.
Economic Minerals
As previously noted, many economic minerals have been mined
from the Black Hills pegmatites. Early in the Black Hills history, the
pegmatites led the nation in lithium and beryl production, was the only source
of columbite-tantalite, and produced about one third of the nation’s mica
requirements. Some highlights of mineral history are provided here:
Columbite to 2cm - Tin Mountain mine.
Don Parsons specimen, Tom Loomis photo.
Beryl
Although beryl is an uncommon mineral worldwide, it is
common in the Black Hills. Lincoln (1927) reported that beryl had been shipped
intermittently from the Hills since 1914. The first economic use of beryl from
the Black Hills dates back to 1930, when beryl from the Sitting Bull mine was
mined and sent to Brush Beryllium Corporation in Cleveland, Ohio. A great amount
of research was under way during this time. Beryllium, as early researches had
known, possessed the tinsel strength of steel and was only slightly heavier then
manganese. The metal is also lightweight, and does not oxidize.
Beryl was and still is the primary source of beryllium and was highly
sought after for its unique qualities similar to aluminum. Early applications
included the use of beryllium nitrate in the manufacture incandescent gas
mantles to harden the mantle skeleton. Beryllium oxide was used as a component
if certain abrasive materials and also in dental cements (Connolly and
O’Harra, 1929). The Bureau of Mines during the late 1920’s was actively
researching beryl, as was the Bureau of Standards, National Advisory Committee
of Aeronautics. Alloys of beryllium with copper, iron, nickel, gold and silver
was also researched during the 1920’s. Beryllium
can also absorb a great amount of heat and dissipate it rapidly. This property
was called “heat sink” and applied to aviation, space flight for re-entry,
and missiles. The beryl deposits in the Hills was the largest domestic source
during 1943-44, when approximately 500 tons were mined from 68 mines. Beryl
peaked in 1953, when 392 short tons were produced from Black Hills mines
(Miller, 1959). A. I. Johnston, a well-known Black Hills mining engineer
described one of the first uses of beryl (Johnson, 1989):
“The mineral beryl became of strategic interest
during the second world war as a source of the metal beryllium which was used as
a moderator in the mechanics of setting off an atomic explosion. By slowing down
the speed of neutrons entering the uranium nucleus an unstable condition
developed in the uranium atom resulting in its disintegration of the uranium
atom and thus releasing the great energy stored up in the atom. Hence an intense
effort on the part of the U. S. government to develop reserves of the mineral
beryl or other beryllium minerals resulted in the concerted effort to develop
increased tonnages from the Black Hills. The price rose to $600 per ton for 10%
ore and was proportionately higher for higher-grade ore.”
Modern uses include alloying beryllium with copper and used
in the defense and aerospace industries as lightweight structural materials in
high-speed aircraft, missiles, and spacecraft. Beryllium is also used in x-ray
technology, computers, and in the nuclear industry.
Tullis in 1952 on assignment from the Bureau of Mines
reported that most of the deposits in the Hills contained less than one percent
beryl. Although Tullis reports that beryl characteristics and quantities can
vary in the Hills:
The size and form of beryl
crystals depend on the zone in which they are found. Small crystals vary from 1
inch in diameter and several inches long. Shell-like
crystals of beryl are found in hexagonal form, consisting of single or multiple
shells enclosing a mixture of other minerals, usually quartz and feldspar….
A number of very large crystals and masses of solid beryl have
been found, and these may contain several tons each.
Tullis (1952) lists 175 mines in the Hills, which contain
beryl to some extant. Roberts and Rapp (1965) listed 36 notable localities. In
the Black Hills excellent crystals groups have been found at the Crown Mica mine
as superb white to pale green doubly terminated crystals up to five inches in
diameter. At the Ross mine near Custer, beryl crystals up to five feet long have
been mined. Huge crystals to ten
feet or more and several tons in weight have been mined from the Tin Mountain,
Ingersoll, Big Chief and many other mines. The Peerless mine was the largest
producer followed by the Ingersoll during the 1920’s (Lincoln 1934). Gem grade
beryl is rare in the Hills but Roberts and Rapp (1965) note a few localities.
These include gem quality bottle green crystals from the Wonder Lode, gemmy
green crystals from the Elkhorn mine, and gem quality sea-green aquamarine at
the Helen Beryl. Most crystals are commonly terminated with basal pinacoids and
very few have complex terminations
Feldspar
According to Connolly (1929), feldspar came on the Black
Hills market in 1923 when freight rates dropped and permitted competition with
eastern supplies. The principal use for feldspar was in the ceramic industry.
Other uses included enameling for metal, glazes, and abrasives in soaps.
The principal variety of feldspar is microcline, although albite occurs in
abundance. The largest producers during the peak years were the Hugo, Big Chief,
White Elephant, Nevins, and the Shamrock. During
World War II annual production averaged 70,000 tons.
The peak occurred in 1946, when about 75,000 tons were produced. During
these years South Dakota ranked second to North Carolina in production (Miller,
1959).
Lithium
Lithium from the Black Hills occurs in
spodumene, amblygonite-montebrasite, lepidolite and triphylite. According to Page et al
(1953), the occurrence lithium minerals are strongly dependent upon the
compositional zones and fracture units of the pegmatites. Spodumene has been
produced from all zones, although amblygonite occurs only in the intermediate
zones and lepidolite only from cores zones. Spodumene was first produced at the
Etta pegmatite in 1898 and sent to Omaha for experimentation. During the
1920’s the Etta mine was the principal producer of lithium in the United
States. Virtually every reference to lithium bearing pegmatites mentions the
huge spodumene crystals at the Etta. Prior to their discovery at the Etta,
two-foot spodumene crystals found in New England pegmatites were considered
“enormous”. The first reference to the spodumene “logs” at the Etta was
by Blake in 1883 (see the Harney Peak article in SD issue I).
Frank Hess in 1939, investigating rare minerals for the Bureau of Mines
described these incredible crystals:
“…huge crystals of
spodumene are mixed at every possible angle like toothpicks in a translucent gel
(quartz). In 1904, a crystal 42
feet long and 3 feet by 6 feet in cross section was found, and the adjective
“enormous” applied to the New England crystals must be transferred. The
crystal weighed about 65 tons.”
It’s interesting to think that in 1819 only half the
elements of the periodic table had been discovered. Lithium was one of the new
elements and was discovered by the young A. J. Arfvedson, a 25-year-old Swede
scientist in 1817. The Swedes were great miners in the early 1800’s and had
already discovered the new elements of cobalt, nickel, manganese, tungsten,
molybdenum, tantalum, barium, and selenium. Then in 1817, Arfvedson discovered
lithium in petalite, which occurred in a pegmatite at an iron mine. His results
were published in1819 and added to the periodic table shortly there after.
Scientists soon discovered that lithium was a silvery-white metal softer than
talc with a hardness of 0.6 on Mohs scale. Lithium as it was discovered was also
incredibly light weighing only 33.9 pounds per cubic foot compared to 169 pounds
for aluminum! Hess (1939) reports the first use of lithium was probably in
medicine. Evidently people drank lithium water and dissolved the calculi in
their bodies. Lithium water became so popular that a law compelled the sellers
to actually include lithium in the water. (Some things never change). Several
lithia springs were also very popular in the New England states. For years this
was the chief use of lithia. Demand dropped when people finally came to their
senses, and this actually contributed to the closing of the Etta mine for a
short period.
Edison eventually discovered the lithium storage battery.
This usage and other applications such as welding, pyrotechnics, photography,
de-humidifiers, and specialty glass contributed to an increase in demand during
the late 1800’s and early 1900’s (Hess, 1939). A. I. Johnson (1989)
estimated over 50,000 tons of spodumene was mined from the Etta pegmatite.
Lithium hydride was produced from Etta spodumene during World War II and used to
inflate antennae carrying balloons sent up by downed pilots for rescue. During
the war effort, about 15,800 short tons were produced from the Black Hills. The
peak production year occurred in 1951 when 8,600 short tons were produced.
Other spodumene localities in the Hills include the Tin
Mountain mine, which was also noted for large crystals. At this locality
crystals up to 30 feet have been found. Crystals
up to 20 feet occur at the Beecher Lode. Well-defined crystals up to eight feet
occur at the Helen Beryl mine. At this locality Roberts and Rapp (1965) note
that hiddenite – spodumene is suitable for
“first quality faceted gem stones”.
Kunzite has also been found at the Beecher and Tin Mountain pegmatites.
Amblygonite, another ore of lithium, was first produced
from the Hills in 1905 (Guiteras, 1940). Although not as abundant as spodumene
in the Hills, it was easier to extract the lithium from the amblygonite and thus
was more desirable. The Beecher pegmatite was known to contain huge masses of
amblygonite up to 200 tons. However, enormous masses up to 30 feet were found at
the Ingersoll mine and up to 40 feet at the Hugo mine (Roberts and Rapp, 1965).
Lepidolite, according to Connolly (1929) was the third most
important lithium mineral in the Hills. The primary use during this time was for
lithium salts, although it was also used in specialty glass.
Lepidolite was first mined in the Hills at the Ingersoll mine according
to Page et al (1953) in 1922 but was not intensively mined until about 1936.
Lepidolite from the Ingersoll was used for the seventeen-foot lens in the
observatory at Mount Wilson, California (Clow, 2002). Lepidolite operations
ceased at the Ingersoll in 1944. Over 8,000 tons were mined from the Ingersoll
pegmatite. Other notable
occurrences according to Roberts and Rapp (1965) include the Beecher, Tin
Mountain, wood Tin, and the Hugo pegmatites.
Mica
At one time the Black Hills supplied one third of the mica
produced in the United States. Mica was the first commodity to be mined in the
Black Hills at the McMackin mine in 1879. The McMackin produced about 45,000
pounds of mica. Other mines included the Climax, Lost Bonanza, and the New York
mines. During this period, Westinghouse Electric operated four mines near
Custer. Sheet and scrap were the two types of mica mined. Sheet mica was used
primarily for insulating electrical equipment. Specifically it was used in spark
plugs, lamp sockets, radio apparatus, fuse boxes, heating devices and
telephones. Scrap mica was used for roofing, wallpaper, paints, for filler in
rubber such as automobile tires, and lubricants (Connolly, 1929). Annual output peaked at 1.5 million pounds during the period
of 1906 to 1911. Mica mining was
practically nonexistent up until World War II when skilled labor was brought in
from North Carolina. At this time about 175 women were employed in the mica
industry supporting the war effort. Johnson (1989) reports that 135 mines were
in operation during the war and produced anywhere from 20,000 to 75,000 pounds
per mine. Combined total during the war was about 1.1 million pounds.
According to Sterrett (1908) mica crystals in the Hills have a tendency
to occur in flattened or tabular blocks lying perpendicular to the walls of the
pegmatite. Crystals are commonly two to eight inches in diameter and one to five
inches tick. However crystals up to three feet are not rare.
Roberts and Rapp (1965) described a book of mica at the White Spar mica
mine three feet wide by four feet long. Also,
at the Red Deer mica mine sheets six feet long by one foot wide have been mined.
The Diamond Mica mine south of the Hugo has long been a favorite of Black Hills
collectors where “fine hexagonal and diamond shaped single crystals” occur.
Other notable mica mines are the Old Mike, St. Louis, Firestone, and the
Galesburg.
Quartz
White or clear quartz has not been produced in the Black
Hills to any significance. Although commercial quantities exist, the Hills were
too far from the market for economic viability. However, rose quartz has been
and still is mined for ornamental and decorative purposes. Lincoln (1927) notes
that Dr. W. P. Jenney brought back specimens on his return from his first
expedition to the Black Hills in 1875. The mineral was first exploited in 1889.
The Scott Rose Quartz mine discovered in 1902 by Samuel Scott is one of the most
famous and probably the longest producing pegmatite in the Black Hills. Edna
Scott, wife of the late Samuel Scott, in her 1941 article in Rocks and Minerals
states that her mine shipped about 1,000 pounds of rose quartz for 25 years to
Germany. The author has recently visited the mine, which is still operated by
the Scott family. The great grandson of Samuel Scott, Carl Scott, operates the
mine intermittently and ships to several localities all over the country. Twenty
to thirty foot wide veins of rose quartz can still be seen in the walls of the
mine. The company report indicates a reserve of about 107,500 short tons.
There are countless other localities of rose quartz in the
Black Hills. The White Elephant, Bull Moose, and the Wiley mines are the most
notable. According to Larsen and Honert (1977), Idar-Oberstein in Germany cut
hundreds of tons of rose quartz into beads, spheres, bowls, tabletops, lamps,
and jewelry. A 3300-pound boulder from the White Elephant was cut into several
large tabletops to 18 x 30 inches. An exquisite bowl was carved from the
Scott’s rose quartz and is still on display at the field museum in Chicago.
The Wiley mine rose quartz has been shown to produce asterism when cut
and polished. According to Hurlbut (1970) rose quartz from the Black Hills was
used to mark the grave of Ralph Waldo Emerson in Concord, Massachusetts.
The Spodumene Problem
Early in the history of mining
pegmatites, geologists have
pondered the origin and theories of formation. In 1933, Kenneth Landes,
published a paper in the American Mineralogist titled “Origin and
Classification of Pegmatites”. Landes
hypothesized the formation of pegmatites and discussed the previous theories of
his predecessors. One of the problems, which may not have been adequately
explained was the “spodumene problem”.
The question was: How did the enormous spodumene crystals of the Etta
pegmatite form? Geologists through
the years have offered theories in an intriguing display of speculation without
a committing themselves completely. A few of the excerpts are provided here to
give the reader a little flavor of this interesting problem:
Blake (1883) offered the first explanation:
“In the numerous tin veins
and granitic dikes bearing tinstone in the Dakota tin region all the phenomena
go to show that the minerals of the dikes, the quartz, feldspar, mica, spodumene, beryl,
columbite, tantalite, and other associates of the cassiterite,
were contemporaneous in origin. All
of these minerals appear to have crystallized out of a semi fluid or pasty magma
in which the elements were free to arrange themselves from one side of the dike
to the other, and separate out by slow crystallization.”
Ziegler (1914) somewhat agreed, but thought the
magmatic solution was much less viscous:
“These pegmatites before solidification are very
fluid and are rich in easily fusible and volatile constituents such as water,
boron, tungsten, chlorine, etc., which are held in solution either as gases or
liquids by great pressure. Such watery solution or fusions offer little
resistance to the force of crystallization and if sufficient time be allowed
this force may govern the arrangement of minute crystal particles for such
distances as forty-two feet……”
Connolly (1929) debated previous theories but offered none
of his own:
“An interesting problem is offered by the
exceptionally large crystals of spodumene. If they were formed by direct
crystallization from a magmatic solution, one wonders what conditions prevailed
at the time of their formation. They are much too long and relatively slender to
have supported their weight without breaking if they grew slowly out into an
open cavity. We know that they must have grown very slowly, not from their huge
size, but also from the fact that lithium is not an abundant constituent of the
parent rock away from the pegmatite masses, and therefore must have been
concentrated at a slow rate and over a long period of time”.
In response to Blake’s theory above, Connolly (1929)
further states:
“But while the crystals were thus forming what
held them up in the solution from which they were crystallizing? None of them
shows evidence of attachment to the walls of the pegmatite body or to the walls
of an open cavity. The specific gravity of the growing crystals would
necessarily be higher than that of the solution from which they were
crystallizing. A thin watery solution, as postulated by Zeigler, would permit
these spodumene crystals to sink rapidly to the bottom of the pegmatite mass. A
semi-fluid or pasty magma, as postulated by Blake would tend to support the
growing crystals somewhat, but would sink slowly, and in time necessary for them
to grow to the huge size they have attained it is believed they would have sunk
to the bottom of the mass.”
Landes (1928 & 1933) presented the replacement theory:
“The writer believes the spodumene to be of later
age than the minerals of the magmatic phase….Many spodumene crystals occur in
groups with a tendency toward spherical radiation. Hess considers such an
arrangement proof of replacement because the crystals must have been supported
in order to so form. The specific gravity of spodumene is 3.2, and crystals of
this weight would have a constant tendency to sink in magma which was
undoubtedly of considerable less gravity (1928)……The large spodumene logs of
the Etta pegmatite are thought to be replacement products of the first
hydrothermal phase.”
Jahns (1955) was rather critical when summarizing the past
efforts:
“The formation of some
pegmatite minerals by replacement of others has been recognized by several
generations of investigators, but there has been no broad agreement as to the
nature of replacing solutions, their source and time of development, and the
quantitative importance of their effects. This is attributable in part to
contrasting views on the nature of replacement processes, in part to differences
in the interpretation of mineral relationships and in assignments of a
replacement origin to certain minerals, in part to lack of adequate quantitative
data on the distribution and occurrence of pegmatite minerals, and in a large
part to the absence of competent observers at those times when the replacement
occurred”.
Finally, Norton et al (1962) offered the most plausible
solution:
“Large crystals occur in
nearly all zones of every zoned pegmatite, and if they formed by replacement, it
is difficult to understand how the different mineral species forming large
crystals were distributed among the zones in such a fashion as to form a
consistent zonal sequence …The large crystals…may have obtained their
support chiefly from others during crystallization of the pegmatite.”
The Big Chief mine
If the Tip Top mine has competition for variety of
phosphates, quite possibly it’s the Big Chief mine. The Big Chief is type
locality for three minerals: olmsteadite, perloffite, and metavivianite. Bill
Roberts first found olmsteadite at the Hesnard pegmatite near Custer and shortly
after at the Big Chief mine by Milo Olmstead. Moore et al (1976) indicated the
Big Chief was chosen as the type locality since the crystal structure analysis
was done on this material. Olmsteadite possesses a peculiar chemistry as a
phosphate of niobium and tantalum. This mineral is very rare, highly sought
after and very beautiful. Crystals are typically found in siderite matrix as
thin tabular, deep red crystals. Most crystals do not exceed 0.3mm. The largest
crystals do not exceed much more than 6mm, although a group of crystals at the
Museum of Geology in Rapid City measures 1.1cm.
Perloffite was first found at the Big Chief mine and
described by Kampf (1977). The mineral is the iron analogue of bjarebyite and
was named in honor of the well-known mineralogist, Louis Perloff. Perloffite,
like olmsteadite is a very elusive mineral and found with ludlamite and
vivianite as jet black, spear-shaped crystals to less than 1mm, but averaging
0.1mm.
Metavivianite was first found by Dr. David H. Garske of the
South Dakota School of Mines and described in Ritz et al (1974). It was
described as minute leek-green, flat, prismatic crystals intimately intergrown
with dark red kryzhanovskite. Whitmoreite was actually the fourth type locality
mineral found at the Big Chief. Bill
Roberts first found Whitmoreite in 1971, but according to Moore (1974), Gunnar
Bjareby submitted specimens of whitmoreite from the Fitzgibbon pegmatite in New
Hampshire almost simultaneously. Moore snubbed both of the original localities
as superior crystallized specimens collected by Bob Whitmore were later
submitted in 1973. Typical crystals of whitmoreite resemble “floating naval
mines” according to Moore. This is quite true, and micro crystals from the Big
Chief mine are no different. However, whitmoreite also occur as isolated
crystals and randomly scattered groups throughout siderite matrix. Crystals are
amber to greenish-brown with chisel-shaped terminations.
The Big Chief originated as a feldspar mine with a beryl
by-product. It is located about three miles southeast of Keystone and was once
operated by A. I Johnson. It is a zoned pegmatite and lenticular in shape. Other
minerals of interest are goyazite, hopeite, kidwellite, kryzhanovskite,
leucophosphite, ludlamite, messelite, phosphophyllite, phosphosiderite,
scorodite, and strunzite.
Ludlamite - Big Chief mine. 8mm crystals.
Tom Loomis specimen and photo.
The Bob Ingersoll mine
A. I. Johnson (1989) once
called the Bob Ingersoll “a mine with more varieties than Heinz has
pickles”. Johnson is correct in “variety” as a number of different ores
are found at the mine. The Ingersoll was the largest producer of lepidolite in
the Hills and one of the largest producers of feldspar and beryl. Other economic
minerals mined were mica, spodumene, columbite-tantalite, microlite, and
uraninite. Five pegmatites are located on three claims of the Ingersoll mine,
which was originally staked as a mica prospect in 1881 and acquired by the
Harney Peak Tin Company in 1884 (Page, 1953). About 1915, a large beryl crystal
was exposed at the Ingersoll, a nearly perfect hexagon 46 inches across the
face. In 1933, another beryl crystal was exposed. This crystal was nine feet
high and over eight feet wide and produced 24 tons of ore. A picture of this
crystal appeared in the May 1934 issue of Engineering and Mining Journal.
Yet another larger crystal was exposed in 1942. This beryl measured 19 feet long
and five feet wide on one end and tapered to 19 inches at the other end. Dr.
Frank L. Hess of the Rare Minerals Division of the Bureau of Mines during a
short reconnaissance trip in September of 1908 to the Black Hills visited the
mine and wanted to make a national monument of the crystal (Johnson, 1989). The
crystal was eventually mined. The largest crystal of amblygonite was mined at
the Ingersoll measuring 28 feet long and six feet in diameter. Blake (1884)
reported a 20-inch square by 24-inch long columbite crystal calculated to weigh
one ton. Large masses of uraninite have been reported with alteration
“halos” of secondary uranium minerals such as becquerelite,
fourmarierite,
and vandendriesscheite. A. I. Johnson (1989) reported a 350-pound mass of
uranium five inches in diameter and two inches thick containing thick yellow and
red alteration rims of the aforementioned minerals. In 1967, a mass of löllingite
25 by 18 by 12 inches in size, weighing 604 pounds, composed of well-formed
prismatic crystals to 12 inches was found (Roberts, 1969). According to Roberts,
this was the largest mass of löllingite ever recorded at a pegmatite.
For years the Ingersoll
was a favorite of mineral collectors. Roberts and Rapp (1965) report several
species at the mine one of which is rubellite and indicolite tourmaline. The
rubellite is found in lavender lepidolite and can occur in gem quality.
Löllingite, jahnsite, fairfieldite, uranophane, kasolite, and autunite are also found.
During a field trip in May, 1969, the Rapid City mineral club headed by Bill
Roberts took a field trip to the Ingersoll mine. Roberts with a sense of humor
described the field trip in the club’s newsletter, the Black Hills Prospector:
“ Several carloads
of avid collectors assembled at the City auditorium at 9:00 a.m., on Sunday May
25th for a field trip to the Ingersoll pegmatite mine near Keystone.
Permission to collect at the mine had been obtained previously by field trip
chairman Frank Tinsley (Tinsley, would later have the mineral Tinsleyite
named in his honor.) …The
Sunday field trip group arrived at the mine at 9:30 in the morning and
immediately started climbing all over the mine dumps like giant ants. Soon after
arrival at the mine, many collectors were somewhat baffled by very a
high-pitched sound which alternately increased and decreased in intensity.
Several of the members furtively glanced around fully expecting to find a
grounded flying saucer or some other diabolic mechanism. Their expectations were
shattered when they discovered that the source of their speculation was Everett
Rambow giving his metal detector a workout.
Vivian Sichterman
found one superb cabinet specimen consisting of several fine olive green
tourmaline crystals on cleavelandite. Frank Tinsley and Milo Olmstead (Olmsteadite)
spent most of their time in a somewhat futile search for good micro material:
they found a few good siderite and albite micros, and one iron manganese
phosphate mineral that has not yet been identified. The Yargers divided their
time between bird watching and mineral collecting: it was rumored around that
they discovered a new species called “zircon crested albite basher”.
After lunch the day
turned extremely hot and the Robesons and many others in the group sought
temporary relief from the sun by frequent visits to the cool tunnel leading to
the upper mine. Jean Roberts found a fine chunk of black cassiterite in white
cleavelandite, plus green, pink and blue tourmaline crystals, and pink cesium
beryl: Bill Roberts found a large chunk of purple lepidolite with half-inch
inclusions of uraninite partially altered to bright yellow, orange and red
secondary minerals.
The last stragglers
reluctantly left the mine about 5:00 p.m., hot, thirsty, sun-burned, and tired,
but well-pleased with their “loot” and grateful to Frank Tinsley for
organizing such a pleasant and productive field trip.”
The Hugo mine
The Hugo mine, located near Keystone, is also directly west
of the Etta mine. The Hugo pegmatite was discovered during a search for tin.
However, the principal mineral in the early life of the mine was mica (Guiteras,
1940) and amblygonite (Norton, 1962). After 1924, about 200,000 tons of feldspar was produced (Guiteras, 1940). This mine was the first to produce potash feldspar in the
Hills. The mine also produced spodumene, columbite-tantalite, and beryl. The
Hugo is a complicated pegmatite, and the knowledge gained from the study of this
pegmatite has clarified many problems concerning the internal structure and
genesis of zoned pegmatites (Norton, 1962). There are seven zones and
replacement bodies, which introduced minerals along fractures. Like the Etta,
the Hugo also contained large spodumene “logs” to six feet. Many other
minerals have crystallized to a huge size, such as a two-ton manganoan
fluorapatite (Campbell, T. J. and Roberts, 1985) and 40-foot amblygonite
crystals. Smith and Fritzsch (2000) lists 34 different minerals found at the
Hugo. This list includes augelite, morinite, and wardite all rare minerals for
the Black Hills. The Hugo is also co-type locality for cern?ite.
Tin Mountain mine
The Tin Mountain mine is
located about 8 miles west of Custer. The claim was patented in 1889 by the Tin
Mountain Company and acquired by the Maywood Chemical Company in 1928.
The claim was originally staked for tin, but unlike the name implies, not
much tin was ever produced. Spodumene, amblygonite, beryl and pollucite were all
produced at the mine. Pollucite masses up to six feet across were found and was
quite different from that found elsewhere in the world. According to Connolly
(1929) the pollucite is “instead of being clear and colorless, as is
usually the case, it is translucent to opaque, very fine grained and white in
color”. Beryl at the Tin Mountain can occur as a clear, limpid, very pale
pink irregular masses, which fooled earlier geologist thinking it was pollucite.
Spodumene occurs at the Tin Mountain as 30-foot crystals. Occasionally kunzite
of light pink grade can be found at the Tin Mountain mine. Exceptional sharp
reddish brown crystals of pyramidal zircons are found at the mine to 2 inches.
Other notable minerals according to Smith and Fritzsch (2000) include
aurichalcite, autunite, bismuth, kasolite, and uranophane.
Tin
Mountain mine, Custer in 2001.
Old Ore
Shoot at the Tin Mountain in 2002.
Other Mines
Other pegmatites in the Keystone area worthy of note
include (Smith and Fritzsch, 2000): the Barker-Ferguson for the type locality
sinkankasite plus fluellite, ludlamite, phosphuranylite, torbernite, and
vivianite; the Champion pegmatite for the type locality of johnwalkite; the Dan
Patch for fluorapatite and ludlamite; the Hesnard for olmsteadite,
phosphosiderite, tavorite and vivianite; the King Lithia for fluorapatite; the
Nickel Plate for arrojadite; the Peerless for fluorapatite, kesterite,
libethenite, mushistonite, struverite, tapiolite, torbernite, and wodginite; the
White Cap for azurite, bertrandite, childrenite, ernstite, fluorapatite,
lazulite, ludlamite, olmsteadite, phosphosiderite, vivanite, and whitmoreite.
Barker mine near Keystone in 2000
White Elephant mine near Custer in 2000.
Old Mike near Custer mine in 2001
In the Custer area, additional pegmatites of note include
(Smith and Fritzsch, 2000): the Bull Moose for barbosalite, fairfieldite,
hureaulite, kryzhanovskite, leucophosphite, ludlamite, phosphoferrite,
phosphosiderite, Reddingite, strengite, tavorite, and vivianite; the Custer
Mountain Lode for autunite and hureaulite; High Climb for laueite; Rock Ridge
mine for rosemaryite; Ross mine for beryl, torbernite and uraninite; the
Shamrock for “watermelon" tourmaline; and the White Elephant mine for
type locality walentaite.
Special Note
Please note: Access to most of the mines in the Black Hills
are restricted if not all together forbidden. Most of the mines mentioned in
this article are within private property and permission must be given by the
landowner for entry. In many cases the entry will be denied. As with all mines,
dangerous conditions exist. Holes, rock walls, shafts, water hazards, equipment,
blasting material, large boulders, dangerous rock slopes and many other hazards
endanger your safety. The author and any aforementioned groups and /or
organizations including MATRIX magazine will not give permission to enter any
mine property and thus will not assume any liability whatsoever.
Fluorapatite - King Lithia mine. Crystals to
2mm.
References
Blake, W. P. (1884) Transactions of the American Institute
of Mining Engineers Vol. XIII: “Tin Ore Veins of the Black Hills”.
Blake (1884) Columbite in the Black Hills of Dakota. Engineering
and Mining Journal, Nov. 11, p. 362.
Blake (1885) Tin ore in the Black Hills of Dakota. United
States Geological Survey Mineral Resources of the U. S.
1883 – 1884, P. 592 – 640.
Campbell, T. J. and Roberts, W. L. (1965) Mineral
localities in the Black Hills of South Dakota, Rocks and Minerals v. 60,
n. 3.
Clow, R. L. (2002) Chasing the glitter, Black Hills
milling 1874-1959: South Dakota State Historical Society Press, Pierre,
South Dakota.
DeWitt, E., Redden, J. A., Burack Wilson, A., and
Buscher,
D. (1986) Mineral resource and geology of the Black Hills National Forest, South
Dakota and Wyoming. United States Geological Survey Bull. 1580
Gries, J. P. (1996)
Roadside Geology of South Dakota, Mountain Press Publishing Company,
Missoula, Montana.
Guiteras, J. R. (1940) Mining of feldspar and associated
minerals in the southern Black Hills of South Dakota. United States Department
of Interior, Bureau of Mines, IC 7112.
Hess, F. L. (1939) Lithium. United States Department of
Interior, Bureau of Mines, IC 7054
Hurlbut Jr., C. S. (1970) Minerals and Man. Random House,
Inc., New York, New York.
Jahns, R. J. (1955) The Study of
Pegmatites. Economic
Geology, Fiftieth Anniversary Volume.
Johnson, A. I. (1989) Western Mining in the Twentieth
Century, Oral History Series. University of California, Berkeley, California.
Kampf (1977) A new mineral:
perloffite, the Fe3+ analogue
of bjarebyite. Mineralogical Record v. 8 p. 112-114.
Landes, K. L. (1928) Sequence of Mineralization in the
Keystone, South Dakota pegmatites. American Mineralogist v. 13, p. 519.
Landes, K. L. (1933) Origin and Classification of
Pegmatites. American Mineralogist v. 18, n. 2.
Larsen, P. and Honert, J. (1977) Rose Quartz of the Black
Hills. Lapidary Journal v. 31, p. 534.
Lincoln, F. C. (1927) Pegmatite mining in the Black Hills. Engineering
and Mining Journal v. 123, n. 25.
Miller, R. H. (1959) Mineral Resources of South Dakota.
South Dakota Industrial Development Expansion Agency.
Moore, P. B. (1973) Pegmatite phosphates: descriptive
mineralogy and crystal chemistry. Mineralogical Record v. 4, n. 3.
Moore, P. B. (1964) Notes on some Black Hills phosphates. American
Mineralogist v. 49, p. 1119.
Moore, P. B., Kampf, A. R., and Irving, A. J. (1974)
Whitmoreite, a new species: Its description and atomic arrangement. American
Mineralogist v. 59, p. 900.
Moore, P. B., Araki, T., Kampf, A. R., and Steele, I. M.
(1976) Olmsteadite, a new species. American Mineralogist v. 61, p. 5.
Norton, J. J., Page, L. R., and
Brobst, D. A. (1962)
Geology of the Hugo pegmatite Keystone, South Dakota. United States Geological
Survey Professional Paper 297 – B
O’Harra, C. C. (1902) The mineral wealth of the Black
Hills: South Dakota School of Mines Bull. 6
Page, L. R. and others (1953) Pegmatite Investigations
1942-1945, Black Hills, South Dakota, Geological Survey Prof. Paper 247.
Pecora , Fahey (19XX)
Am Min
Petar, A. V. (1929) Beryllium and Beryl. United States
Department of Interior, Bureau of Mines, IC
6190.
Ritz, C., Essene, E. J., and
Peacor, D. R. (1974) Metavivianite, a new mineral. American Mineralogist v. 59, p. 896.
Roberts, W. L., and G. Rapp Jr. (1965) Mineralogy of the
Black Hills. South Dakota School of Mines bulletin 18.
Roberts, W. L. (1969) Ingersoll field trip. Black Hills
Prospector v. 2, n. 6.
Scott, S. S. (1897) Rocks, Minerals, and other Resources of
the Golden Black Hills of South Dakota and Wyoming. Custer, South Dakota
Scott, E. M. (1941) Scott Rose Quartz mine. Rocks and
Minerals, v. 16, n. 10.
Smith, A. E. and Fritzsch, E. (2000) South Dakota mineral
index. Rocks and Minerals v. 75, n. 3.
Sterrett, D. B. (1908) Mica Deposits of South Dakota,
United States Geological Survey Bull. 380N.
Triscori, K. L. and Campbell, T. J. (1986) Type locality
minerals of the Black Hills, South Dakota. Mineralogical Record v. 17, n.
5.
Tullis, E. L. (1952) Beryl resources in the Black Hills,
South Dakota, United States Department of Interior, Bureau of Mines, RI 4855.
Ziegler, V. (1914) The minerals of the Black Hills. South
Dakota School of Mines bulletin 10.
Zodac, P. (1953) World news on mineral occurrences – note
form David Seaman about South Dakota. Rocks and Minerals v. 28, n. 3-4.
|
