In wandering through my
collection of minerals brought home from the 2016 Tucson Show, I came across a
specimen of emmonsite. I reached to the
back recesses of my mind trying to remember why I purchased such a specimen. Yes, it is a nice green-yellow color and looked
interesting under the loupe but then I remembered—I was going to check and see
if emmonsite was named for the famous geologist Samuel Franklin Emmons. Well, I finally got around to checking and
sure enough emmonsite [Fe2(TeO3)3-2H2O],
a fairly rare iron (ferric) tellurite, was named for a well-known geologist
that Colorado has sort of claimed as a native son (although he was born in
Boston in 1841 and descended from a long line of native Bostonians—lineages arrived
in the 1630s), or at least a favorite son.
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| S.F. Emmons, ca. 1860s. Photo courtesy of Library of Congress. |
The following information
is abstracted and interpreted from Hague (1912) who wrote a “Biographical Memoir”
of Emmons published by the National Academy of Sciences. Emmons was one of those “old fashioned” geologists,
attending private primary and secondary schools in Boston and finishing up at
the Dixwell Latin School. Emmons was
educated to become a gentleman of broad culture, refined manners, and to enter Harvard
University, which he did at age 17, and graduated in 1861. When I first read “1861” I wondered why he
did not enlist in the U.S Army since Harvard furnished a number of students to
the anti-slavery movement. Hague (1912)
noted that Emmons’ father persuaded him to pursue a professional career, rather
than to follow many classmates into military service. To further discourage enlistment (I presume),
Emmons was sent by his father, after graduation, to Europe in order to accompany
his mother on a health recuperation trip.
He seemed to have spent the summer of 1861 climbing mountains and
hiking, and presumably taking care of his mother. She sailed back to the States in November while
Emmons toured London and ended the year in Paris. In the City of Eternal Light, Emmons spent nine
months working under private tutors in order to relearn French and prepare for
entrance exams to the prestigious Ecole Imperiale des Mines (School
of Mines). Emmons spent two years at the
School of Mines and then decided he wanted to get a more practical mining
experience (hands-on) so spent the next year (1865) at the Bergakademie (Mountain
Academy) at Freiberg, Saxony, Germany (where there were mines at the city
limits). After leaving Freiberg, Emmons
spent the winter in Italy and finally returned to Boston in June 1866 (probably
to the delight of his family since the conflict was over).
As a graduate student at the
University of Utah, I fell “in love” with reading about the geological exploration
of the American West via the Great Surveys:
F.V. Hayden and the United States Geological
Survey of the Territories; Clarence King and the Geological Exploration of the Fortieth Parallel; John Wesley Powell
and The Exploration of the Colorado River and its Canyons; George M.
Wheeler and the many volumes of Explorations
and Surveys West of the 100th Meridian. These surveys of the western United
States ultimately were reorganized (1879) into the United States Geological
Survey.
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| A "Great Surveys" volume picked up at a garage sale 50 years ago. |
This was an exciting time
to be at the University since the senior instructors were only a couple or three
generations removed from the early western geologists and had traversed the wide-open
spaces of the west when it was still “wild.”
They had been trained as classical geologists (mostly in the eastern
U.S.) and tried to impart their thoughts
to the students, especially the need for precise field work. Our field trips often were taken to areas
touched by Great Surveys. I sort of fell
into a trance standing at the entrance to Ladore Canyon on the Green River
trying to imagine what John Wesley Powell felt as he guided his small boats
into the “great unknown.” Students were
greatly impressed with the detective work of Clarence King (including Emmons)
and his geologists in debunking the great diamond find in northwestern Colorado
and we wondered if a ruby or diamond still were to be found? Alas, no luck.
But back to Emmons (following
Hague, 1912). Upon returning to the
States Emmons secured a job, at first as an unpaid volunteer, with the King
Survey and they sailed for California in May 1867. He later was hired as an
assistant geologist and Hague (1912) noted that Emmons “was full of youthful
spirits and manly exhilaration over the work before us.” Emmons
worked for 10 years with various aspects of the King Survey that perhaps
culminated with the publication (890 pages) of descriptive geology. I did not realize (no surprise here) that after
leaving the Survey Emmons “engaged actively in cattle ranching, and for some
time made his home in Cheyenne, Wyoming.”
In 1879, the U.S. Congress
created the Bureau of the Geological Survey (the USGS) and Clarence King was
appointed the first director on April 3.
On August 4 of that year King appointed Emmons as “Geologist in Charge
of the Rocky Mountain Division” and a mandate to devote his first years to “a
study of the mineral wealth of the Rocky Mountains.” In 1886, Emmons was the lead author of USGS Monograph
XII, Geology and Mining Industry of
Leadville, Colorado with Atlas (~779 pages). Hague (1912) noted that it “won for its
author an international reputation…probably no single publication of the
geological survey has exerted a more beneficial influence and stimulated more
discussion.” Professional geologists
could ask for little more than an accolade like that.
After Leadville Emmons
lead an active geological life with an amazing number of papers on a wide
variety of subjects, including: On glaciers
in the Rocky Mountains; Notes on gold
deposits in Montgomery, County, Maryland; Geology of the Tintic Special District, Utah. In Colorado Emmons is remembered for
excellent papers on Colorado ore
deposits, Geology of Aspen Mining District, Geology of the Elk Mountains, Geology
of Rosita and Silver Cliff and Mines
of Custer County, Geology of the Denver Basin, and Geology of the Ten Mile District. I would encourage interested readers to
observe his bibliography (Hague, 1912) found at: https://books.google.com/books?id=vZ0aAAAAYAAJ&as_brr=4&pg=PA309#v=onepage&q&f=true. In addition to his publications, Emmons was
one of the founding members of the Geological Society of America and served as
the President in 1903.
Also of interest to
Colorado scientists: (in the history of the Colorado Scientific Society, the
oldest scientific society in the Rocky Mountain region at www.coloscisoc.org. On the evening of December 8th, 1882, a number
of gentlemen interested in the formation of a scientific association met in the
rooms of the United States Geological Survey, in Denver, at the invitation of
Mr. Samuel Franklin Emmons.” “Mr. Emmons, in stating the object of the meeting,
said that it seemed to him that the time had come for those persons in Colorado
who were interested in true science to unite in forming an association or
society, whose immediate object would be to facilitate the interchange of
scientific observations and ideas, and promote intercourse among the observers
themselves. There should be some means of recording and publishing the many
interesting and valuable facts which are daily observed in different parts of
the State. This could be done through the medium of a society, and the
opportunity thus afforded would no doubt act as a stimulus to some to pursue
investigations in directions specially open to them.” “An informal discussion
ensued in which the advisability of such a step was advocated, and it was agreed
to proceed at once to form a permanent organization.” “The following named
persons were unanimously chosen as officers for the first year:
President—Samuel Franklin Emmons Vice-President—Richard Pearce
Secretary—Whitman Cross.”
Although Emmons was not a
“Native Coloradoan” his work certainly qualified him as perhaps the most respected
geologist in in the state’s history. Emmons
was active until his death in 1911. Hague
(1912) noted that “he left a noble record of life’s work well performed.”
Among other honors
bestowed on Emmons, Colorado designated a 12,401-foot peak near Crested Butte in
the West Elk Mountains as Mt. Emmons.
Not to be outdone, Utah designated a 13,448-foot peak in the High Uintas
Wilderness as Mt. Emmons. Interestingly,
the Utah peak is connected by a rugged ridge to the highest peak in Utah, Kings
Peak at 13,534 feet. So, even in death Emmons
and his long-time friend and colleage, Clarence King, remain connected.
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| Mt. Emmons, Colorado, 12,401 feet. Photo courtesy Google Earth. |
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| Mt. Emmons, Utah, 13,448 feet. Photo courtesy Google Earth. |
This offering started out
about the mineral emmonsite and so it will finish with the same. Emmonsite is one of a few minerals that
contain the element tellurium, a silver-white metalloid (possesses properties
of both metals and non-metals). Tellurium is an extremely rare element as most
rocks contain about 3 parts per billion and is 8 times less abundant than gold
(Goldfarb, 2014), and is related to selenium but may be only mildly toxic! Tellurium is rarely found in a native form.
Tellurium can act as a
cation with a 4+ oxidation state as in the uncommon mineral tellurite, TeO2, or
with a 6+ oxidation state as in jensenite, Cu3TeO6-2H2O The
telluride anion with a charge of 2- can combine with gold and silver cations in
the minerals calaverite (AuTe2) and sylvanite (AuAgTe4). These telluride minerals form major gold ores
at Cripple Creek, Colorado. So, it is
confusing when one talks about tellurium, tellurite, and telluride.
Emmonsite [Fe2+++(Te++++O3)3-2H2O;
a hydrated iron tellurite, occurs in a wide variety of habits from microscopic
druses, to hair-like masses, sprays, compact masses, globs, and small acicular
crystals. I could not locate information
on larger than microscopic crystals but MinDat lists emmonsite as belonging to
the Triclinic System. It has a green to yellow-green color, vitreous to subvitreous
to even dull luster, opaque to translucent to transparent diaphaneity, and is
reasonably hard at ~5.0 (Mohs). Its
characteristic yellow-green color combined with the often branching
(coral-like) or fungus-like shape are the best identifying marks. Emmonsite is a secondary mineral found in the
oxide zones of hydrothermal tellurium-bearing base minerals. It is often found with native tellurium and
the telluride minerals.
 |
| Green, fungal-like habit of emmonsite. Length main "mass" of mineral ~4 mm. |
Hillebrand (1885) gave
the type locality of emmonsite as Tombstone, Arizona. As described by Pearl
(1941), the discovery of a new mineral
which he named emmonsite in honor of Samuel B. Emmons, first president of the
Colorado Scientific Society and one of America's outstanding geologists, was
told by W. F. Hillebrand at the meeting of the society at the Arapahoe County
(now Denver) Court House on June 1, 1885. The mineral had been sent by R. C.
Hills from an uncertain locality near Tombstone, Arizona Territory. So, it
would seem that Emmons was (may have been) at the Colorado Scientific Society meeting
when Hillebrand gave his description of emmonsite.
Hillebrand (1904) also
described emmonsite(?) from Colorado and in Bulletin 262 of the USGS (1905)
stated a green mineral was collected at the W.P.H. Mine at Cripple Creek that
showed a close resemblance to emmonsite he described 20 years ago (the specimen
from Tombstone). However, Williams
(1980) believed that the mineral described from Tombstone actually was
rodalquilarite, a hydrogen iron tellurite chloride. Eckel and others (1997) then believed it would
then make sense to declare the mines at Cripple Creek, Colorado, as the type
locality for emmonsite. However, I note
that MinDat still lists Tombstone as the type locality.
My specimen of emmonsite was collected from the Bambolla
Mine (Montezuma Mine) located in Municipio de Moctezuma, Sonora, Mexico. I have been unable to locate much information
on the Mine other than in the 1970s, it was a producing gold mine. I assume, that like nearby mines,
mineralization was related to hydrothermal activity associated with Tertiary
volcanic action. However, the amazing
information is that the Mine, and the nearby (half mile away) Bambollita Mine,
are the type localities of at least 23 tellurium-bearing minerals! Also, I stumbled upon an article, actually a discussion,
of a micro-mineral group (Associazione
Micro-mineralogica Italiana). Luckily,
the discussion was in English! At any
rate, Ciriotti (2010) noted: Oxide-zone
tellurium minerals are relatively rare worldwide… 71 known Te-oxide minerals, 68 of which are
considered valid species; most are either tellurite (Te4+O3)2- or tellurate
(Te6+O6)6- species… over 60% of the species (43 out of 71) were discovered
at only four deposits: Moctezuma, Mexico; Tombstone, Arizona; Centennial Eureka
Mine, Utah; and Otto Mountain, California. In fact, nearly a third of all Te-O
mineral species were discovered in just one deposit: Moctezuma. Many of these
species are still found at only one locality today… The four
leading occurrences listed above are all oxidized base metal deposits, and not
surprisingly, 60% of all Te-O minerals contain Pb and/or Cu. If Zn and Fe are
added in, this increases to 84%... And
that sort of sums up my limited knowledge about tellurium minerals.
This is one of those
postings that started out as a simple discussion of the Colorado Scientific
Society and its first president S. F. Emmons.
However, it morphed into the fascinating world of tellurium and the
resulting minerals. I am still trying to
digest some of the information but needed to draw a conclusion line---somewhere! Unfortunately, the length and breadth of the subject
may turn off all but the most dedicated readers and for this I apologize. But, just as a dog worries a bone I worry a
subject that I don’t really understand. The
good thing is that “new learning” is a joy for me and hopefully keeps my brain
alive. My philosophy about learning may be summed up by two rather famous
individuals:
Anyone who stops learning is old, whether at twenty
or eighty. Anyone who keeps learning
stays young. Henry
Ford
Every time I learn something new it pushes some old
stuff out of my brain. Homer Simpson
REFERENCES
CITED
Ciriotti, M.E., 2010,
Oxidation zone tellurium minerals: Associazione
Micro-mineralogica Italiana. http://forum.amiminerals.it/viewtopic.php?t=7168.
Eckel,E.B. (and others), 1997,
Minerals of Colorado: Denver, Fulcrum Publishing.
Goldfarb, R., 2014,
Tellurium—the bright future of solar energy: USGS Fact Sheet 2014-3077.
Hague, A., 1912,
Biographical memoir of Samuel Franklin Emmons, 1841-1911: National Academy of
Sciences, Biographical Memoirs, v. VII.
Hillebrand, W.F., 1885, Emmonsite,
a ferric tellurite: Colorado Scientific Society Proceedings, v. 2, pt. 1.
Hillebrand, W.F., 1904, Emmonsite(?)
from a new locality: American Journal of Science, 4th Series, v. 18,
no. 108.
Hillebrand, 1905, Two
tellurium minerals from Colorado: U.S. geological Survey Bulletin 262.
Pearl, R.M., 1941,
Minerals named for Colorado men: Colorado Magazine, v. 18, no. 2.
Williams, S.A., 1980, The
Tombstone district, Cochise County, Arizona: Mineralogical Record, v. 11, no.
4.
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