REMEMBERING UTAH AND A THALLIUM ARSENIC SULFOSALT: GILLULYITE

 BLOG POST # 500 😊😊😊

In several of my Blog postings I noted that my time in graduate school at the University of Utah (1967-1970) was intellectually exciting as well as personally full of satisfaction and “what more could you ask for”. Within a 10-day stint in August 1967 I graduated with an A.M. from the University of South Dakota, drove all night to Kansas with my soon to be wife, got married, and headed to Utah with virtually no money; more grad school was waiting. I chose Utah since: 1) I wanted to live in the mountains; 2) Wyoming and Colorado rejected my applications; and 3) the NDEA Title IV Fellowship at Utah was more money than I had ever made in my life. We were still rather "poor" but found an apartment for $70 a month; however, we could only afford payments of $35 every two weeks! But, we found new friends (mostly students), and we were all in the same boat—not much money but excited about geology and our spouses (most of us were newlyweds).

Intellectually the University was an exciting place to be in the late 1960s—things, they were a’ changing in the world of geology. Plate tectonics, better then known as Continental Drift, was being discussed in every classroom. Armand Eardley had published the best-known textbook on structural evolution of North America, and it was the “go to” book in the pre-continental drift days. However, he constantly brought in external speakers to discuss the “theory” in his classes, the pros and cons.

Fridays were observed as days of field trips and/or research—we could walk to outcrops in the Laramide Wasatch Mountains bordering east campus. Evidence of Pleistocene Lake Bonneville was everywhere, and we could drive 25 miles or less to observe rocks of every geological period except the Silurian. Observing fantastic geology was an everyday experience.

The campus of the University of Utah (2005) next to the Wasatch Mountains. Photo picked up from Pinterest https://i.pinimg.com/originals
 

Lee Stokes, my major advisor, hauled his students all over the state since his Utah geological knowledge was legendary. Jim Madsen, my mentor and friend, was pulling all sorts of dinosaurs out of the Cleveland-Lloyd Quarry in central Utah. Others, such as Dick Robison took his advanced invertebrate paleo students out to the west desert to hunt for trilobites in the Cambrian rocks. We then had to write a “pretend” professional paper for publication. It was just a great time to be a student of geology.

The U.S. Geology Survey had a small office in Salt Lake City and their geologists were tromping all over the Intermountain states. As they traversed through the City the Department tried to nab them to “present a lecture on their work.” I, and my classmates, were privileged to hear, and often meet, some of the most famous geologists in the west. I remember one of the speakers was a USGS scientist by the name of James (Jim) Gilluly. I remembered his name since the grad students were expected to constantly read journals and other professional papers (“you really need to take a look at XX paper since it may show up on your prelim exams”) and one of these papers (USGS PP 150) was authored by Reeside and Gilluly describing the sedimentary rocks of the San Rafael Swell in central Utah. Now the Swell was every softrocker’s favorite place for a field trip---and there were many. Gilluly also worked with Ralph Roberts and others in describing the Antler Orogenic Belt and the giant Roberts Mountain Thrust in north central Nevada (almost unknown events in the 1950s). But perhaps Gilluly’s most interesting paper was published in 1968-- The role of geological concepts in man’s intellectual development. Gilluly lived a long (1896-1980) and extremely productive life, and his name always sticks in my mind when thinking of those halcyon days of the late 1960s at the University of Utah. 

The Oquirrh Mountains viewed from south of Salt Lake City looking west.  Public Domain photo by Don Lavange.

So, how does my reminiscing relate to minerals of any sort? Many/most readers realize that past postings often point out interesting tidbits about Utah minerals, and especially the few related to instructors at the University: check September 17, 2017, for a posting on whelanite, stringhamite, and callaghanite. Well, a thallium arsenic sulfosalt mineral named gillulyite (after the Utah geologist) is certainly an interesting mineral (if nothing else for its thallium content) and one of the rarest in Utah (and most likely in the country). It also has an interesting collecting history, and the following paragraph was picked up from Lehigh Minerals in Bountiful, Utah

“ In 1990 five members of the club, Mineral Collectors of Utah, went on a field trip to the Lulu Cut in the South Mercur Pit of the Mercur Mine in search of thallium minerals.  An odd-looking red mineral that looked different than Realgar was found.  Two members searched for crystals, only ever finding 3 specimens with small crystals.  One of which is pictured on mindat.org .  The three other collectors collected a few flats of specimens of the strange mineral with dark red cleavages.  Dr Jim Wilson from Weber State was one of the three and the analysis done the next day did not match any known mineral species.  Going back the following day to collect more specimens, he was disappointed and found the Barack mining operation mined through the collecting area and the new level was 30 feet below the area of the new mineral find.  Nothing more was able to be collected.  The mineral became Gillulyite with the Lulu Cut being not only the type locality but still the only locality to this day in the world.   One collector sold his specimens at the next Denver and Tucson shows.  These are the source of specimens currently held in collections worldwide.  The mine geologist collected some superb Lorandites at another  location at the mine but was present when the club was there and also had a few Gillulyites.  Scott Klein and Rob Lavinsky handled these several years ago.  I was able to acquire  the specimens that Jim Wilson collected that day.  These vary in size from thumbnails to large cabinet specimens.”

I have recently corresponded with Jim McEwen, the proprietor of Lehigh Minerals and amazingly he still has about seven specimens of this 30-year-old find sort of hidden away, but available for sale! They are listed on the Lehigh Minerals home page.

Gillulyite [Tl₂(As,Sb)₈S₁₃] is a dark red in color like many mercury minerals, is soft at 2.0-2.5 (Mohs), has an adamantine luster that commonly tarnishes to a metallic luster. It needs to be protected from light as the mineral will turn such a dark red that it almost appears black. Crystals (Monoclinic Prismatic) are rare (some crystals shown on MinDat), and most specimens appear massive (and all are small). At Mercur, gillulyite is often associated with baryte (BaSO₄), orpiment (As₂S₃), and realgar (As₄S₄). As a sulfosalt the elements in gillulyite are: a metal (thallium), a semi-metal and/or tin (arsenic + tin), and sulfur---Tl₂(As,Sb)₈S₁₃.

Bright to dark red gillulyite with yellow orange orpiment on a baryte matrix. The width of the baryte in the top photo is ~4mm. The gillulyite fragments are sub millimeter and my camera had a tough time with focusing on the minerals, partially due to the bright refection of the orpiment. At any rate it is an extremely rare mineral from the Lula Cut, South Mercur Pit.
 

The Mercur Mining District is on the southwest flank of the Oquirrh Mountains, one of the easternmost ranges of the Basin and Range Province, that dominates the western skyline at Salt Lake City (and also home to the famous Bingham Copper Mine). The initial mining at Mercur started in ~1870 with a high-grade silver deposit but soon faded and mining turned to cinnabar, the valuable major ore of mercury. Early miners knew that gold was present at Mercur; however, the small flakes were invisible and tied up in dark gray to black carbonaceous, silty limestone. The gold could not be extracted with traditional mercury amalgamation processes (today we know Mercur as a Carlin Type Deposit). About 1890, as the mining was about “done for” a couple of the investors decided to try a new process rumored to be effective—cyanide leaching. And it was successful for by 1897 the Golden Gate Mill at Mercur was the largest cyanide mill in the U.S. and operated until ~1913. After that date the gold production was intermittent with starts and stops by various companies. By 1983 Getty had established a very successful, large open pit with a cyanide heap leach operation. Barrick Gold acquired this operation in 1985, added some additional equipment and produced ~ 100,000 ounces of gold per year until reserves became exhausted in 1995. The mines have now been reclaimed and gillulyite is gone forever from Mercur (the official Type Locality is Lulu Cut, South Mercur Pit) and has never been located elsewhere. As for the Mercur Mining District, it was Utah’s largest primary gold mining district , “despite the fact that no gold was ever recognized in hand specimens” (Utah Geological Survey). I tried to visit the dumps in the early 2000s but was turned away by signs, fences, and “guards.” 

I REMEMBER SPRING 1970

After the invasion of Cambodia in the spring of 1970. After the deaths of four students at Kent State University in Ohio on May 4, 1970, students rioted at the University of Utah. Classes were disrupted, the Daily Utah Chronicle offices were occupied, and the ROTC building was fire-bombed. On May 6, four thousand students gathered for a rally south of the Union Building. During the rally, fire broke out in an abandoned World War II building near the Union. The building was no great loss, considering it saved the costs of razing it, but a short while later 800 students marched into the Park Building and sat down (from the archives of J. Willard Marriott Library). 

Was I in the above photo?  No, the geology grad students were perched on the green lawn eating our bag lunches. We all had theses and dissertations to complete (I missed the spring deadline)!

LATRAPPITE: A RARE NIOBIUM MINERAL

 

Niobium (Nb) is not a chemical element that effortlessly slips off your tongue when asked to quickly name 25 elements. However, it is the 34^th most common element in the earth’s crust. It is less abundant than zinc, nickel, and copper but more abundant than cobalt or molybdenum. That lack of familiarity is probably due to the fact that free niobium is not found in nature; it is always combined with other elements in minerals. Niobium is closely related to the element tantalum and the two are often found together in minerals. In fact, at one time in the early 1800s chemists believed columbium (former name of niobium) and tantalum were the same element. That is one reason that columbite [(Fe,Mn)Nb₂O₆)] and tantalite [(Fe,Mn)Ta₂O₆)] are often confused in the field with each other and the moniker columbite-tantalite (or coltan) is attached to these unknowns. I certainly know that in the pegmatites of the Black Hills of South Dakota most rockhounds refer to these dark minerals as columbite-tantalite since  it is virtually impossible to determine if tantalum or niobium is the dominant cation.

MinDat lists 115 minerals that contain essential niobium, the majority of which are oxides and silicates:  euxenite (Y-REM), fergusonite (Y-REM), columbite, pyrochlore group, lueshite, latrappite, and limonorutile. Commercially most niobium is extracted from ores of columbite-tantalite, pyrochlore group, and euxenite with the largest resources located in Brazil and Canada. The primary niobium ores are oxides of the pyrochlore group and located in carbonatites (magmatic rocks containing more than 50% carbonate minerals) and alkaline-syenite complexes. Carbonatites are usually associated with crustal tectonic rift zones. (Virginia Department of Energy: Virginia Division of Mineral Resources, Publication 115.)

A couple of years ago in Tucson, while rummaging around in a dusty flat of minerals, I came across a specimen of latrappite. The label was “older” and stated “compare to perovskite, same family, these are better. From the Ray Collection.” MinDat (on my phone) informed me I was looking at a mineral containing niobium. Older labels always attract my attention, and often my money,  and a couple of days before I had picked up a specimen of perovskite with a Mineralogical Research Company (CA) label. Now I was ready to examine their relationship—it only took me two years.

Perovskite is a calcium titanium oxide [CaTiO₃] belonging to the Orthorhombic Crystal System; however, it is pseudo cubic and crystals generally have a cubic habit. These small cubes come in a variety of colors from black to brown to shades of yellow, orange and red. My cubes have an adamantine to sub-adamantine luster, are fairly hard at ~5.5 (Mohs) and seem partially translucent (ranges from transparent to opaque).  At times some cubes have a metallic luster and look similar to galena. Niobium is a common impurity in perovskite but not an essential mineral. Anthony and others (2001-2005) noted perovskite forms as an accessory mineral in alkaline mafic rocks, as nepheline syenites, kimberlites, carbonatites, and can additionally form in calcium-rich skarns (such as Magnet Cove, Arkansas), and is a common accessory mineral in calcium and aluminum rich inclusions within carbonaceous chondrites.

Above photomicrographs: cubes of perovskite ~.6 mm along margins. Collected Perovskite Peak, San Benito County, California.

Photomicrograph, cube of perovskite ~ 2mm on edge. Some overgrowth of calcite. Collected from Malenco Valley, Valtellina, Sondrio Province, Lombardy, Italy.

In contrast to perovskite, latrappite is a mineral where niobium is an essential element—Ca₂NbFeO_6. So, what is the relationship between latrappite and perovskite? One simple explanation is that the crystals of both minerals look similar to each other—crystals are Orthorhombic but pseudo cubic and have a cubic outline, cleavage is absent, the colors of the cubes are usually black to dark brown, a hardness of ~5.5 (Mohs), a metallic luster, and generally are collected form carbonatite complexes. A more “scientific” explanation is that the niobium exceeds the titanium in latrappite type minerals. In fact, at one time latrappite was known as niobium perovskite. Due to the analysis by Mitchell and others (2017) the IMA redefined niobium perovskite as latrappite (niobium greater than titanium) from a type locality (Carbonatite Complex), Deux-Montagnes RCM, Laurentides, Quebec, Canada. But it also remains as a mineral of the Perovskite Supergroup. 

A cube of latrappite ~2.4 mm on edge. Collected from the Type Locality, Bond Zone, Oka, Deux-Montagnes RCM, Laurentides, Quebec, Canada.
 

REFERENCES CITED

Anthony, J.W.  R.A Bichard, A. Bideaux, K. W. Bladh, and M. C. Nichols, Eds., 2001-2005, Handbook of Mineralogy, Mineralogical Society of America, Chantilly, VA 20151-1110, USA. http://www.handbookofmineralogy.org/.

Mitchell, R., M.D. Welch, and A.R. Chakhmouradian, 2017, Nomenclature of the perovskite supergroup: A hierarchical system of classification based on crystal structure and composition. Mineralogical Magazine: 81(3): 411-461. https://doi.org/10.1180/minmag.2016.080.156

WHAT TO DO WITH A VOLCANIC PLUG

Painting of Edinburgh Castle ~1780 by Alexander Nasmyth. Public Domain.

The title says it all!  What does one person/state/country do with a volcanic plug? I asked this question to a group of beginning geology students many decades ago. Probably the most common answer was to quarry the basalt (or similar volcanic rock) and use the material for construction aggregate. Since volcanic plugs, or any volcanic material (except bentonite and wind blown ash), are unknown in the superficial sedimentary rocks of Kansas that was a reasonable guess. In further discussions I found that several of the students had seen cinder cone quarries during vacation trips/field trips through New Mexico and/or Arizona. There is a world of difference between cinder cones and volcanic plugs.

Sunset Crater is a large cinder cone located north of Flagstaff, Arizona, in the San Francisco volcanic field. The vent erupted ~1075. Photo Public Domain and courtesy of Mike Sanchez.
 

A cinder cone is a smaller conical hill composed of volcanic ejecta-- loose pyroclastic clinkers, volcanic ash, or scoria—that formed when a volcanic vent “blew” small fragments into the air and as they rained back down the fragments cooled and accumulated in a  cone-like structure.  These small cones are often quarried for construction aggregate, decorative yard rocks, and even for use in “backyard barbecue” grills as a cover for the burners. There is virtually no large-scale solidification of the clinkers, and they literally may be “scooped up” with a shovel or backhoe. Easy to quarry.

A volcanic plug is formed when molten magma hardens in the throat of an active volcano and blocks further eruptions from that particular vent. Sometimes the volcano becomes “unplugged” as massive pressure builds up under the plug and a very explosive eruption takes place—the volcano “blows its stack.”  At other times the pressure in the magma field simply opens a new vent. At other times, as the vents start to cool down, the plug in the throat also hardens into a very tough basaltic type of rock (I use this term to indicate any of the fine-grained, extrusive igneous rocks that form from the rapid cooling of lava rich in magnesium and iron. Some are actually diabase or dolerite or trachyte or a variety of other types). In fact, these throat rocks are often harder than the surrounding country rocks. As time moves on, erosion removes much/most of the surrounding rock and the volcanic plug becomes a positive topographic feature.  There are literally hundreds of these plugs scattered across the world but to me the most impressive are the volcanic plugs scattered across the red rocks of the Colorado Plateau. The most famous plug of the Plateau is probably Ship Rock near the Four Corners area of Colorado, Utah, New Mexico, and Arizona although nearby Agathla Peak, seven miles north of Kayenta, is much more intimate and easier to reach.

Agathla Peak, a volcanic plug, rises about 1500 feet above the desert floor in the Four Corners area.

So, to add a second choice to the question—preserve the plug as a scenic area or state park or wilderness or tourist attraction.

Edinburgh Castle. Public Domain photo courtesy of kids.kiddle.co.

Edinburgh Castle, with associated buildings (including the New Barracks 1799), situated on the summit of Castle Rock, a volcanic plug.

I find a third choice perhaps the most intriguing—build a fortified castle. I recently returned from a two-week train trip, with nightly stops at guest houses or pubs, visiting England and Scotland, from the southwestern beaches of England to North Sea beaches on the Firth of Forth in Scotland (I love the name of that locality). 

The UK has a magnificent high speed passenger rail system. We opted for a rail pass available to U.S. residents and spent a few dollars more for First Class. Wow. Luxury reserved seating with complimentary (somehow I paid for it) food and libations.

 

As most of us know, thanks to British BBC and/or U.S. PBS shows, the UK has numerous castles spread over the country. Some are in ruins while others are in quite good shape although the tremendous monetary expenditures needed for upkeep often necessitate opening the residences for tourist visitation. Most are built on flatlands complete with moats and swans; a few are built on higher points. The most impressive castle I observed on this trip was Edinburgh Castle (Scotland) situated on the high point of Old Town and constructed on Castle Rock. Impressive to a geologist since Castle Rock is a volcanic plug and was incorporated into the foundations of the buildings. In other words, the master stone masons did not “smooth off” the plug but cut dimension stone to fit the varied surface. I suspect that only an ole plugger like me would notice such a masterful piece of work; however, I was really impressed. The Castle was started sometime in the early 1200s; however,  Castle Peak was inhabited several centuries earlier. In the ensuing 1100 years Scotland and England were the sites of almost continuous warfare, and the Castle of sieges, at least 21 according to our tour guide.  Readers need to use a web browser and “look up” Edinburgh Castle.

Stonemasons quarried local limestone and sandstone as well as parts of the plug.

Notice how the building stones "fit" into then topography of the igneous rock foundation.

Soldiers of the Castle Garrison ca. 1845 (Top, Public Domain). A lone guard 2023 (Bottom).

The geological makeup of Scotland is extremely complex and many/most of the country seems composed of small orphan terranes stitched together during plate movements. The volcanoes that produced Castle Rock, and numerous other volcanic features of southern Scotland, are about 350 Ma, early Carboniferous (Mississippian in the U.S.) Period. At that time “Scotland” was part of the Supercontinent Pangaea and situated near the equator. There were periodic incursions of shallow marine waters and the southern Scottish volcanoes evidently intruded, at times, into these shallow seas. Many of the local quarried stones for the Castle buildings are of shallow marine origin of Devonian and Carboniferous age. Pleistocene glaciation helped create most of the modern landscape of Scotland and was critical in shaping the “modern” Castle Rock. As glaciers moved in from the north the volcanic rocks were more resistant to erosion than the surrounding sedimentary rocks and left the plug as a isolated highland. However, the harder plug (a crag) protected the sedimentary rocks on the leeward side and formed a somewhat tapered ramp (tail). The Scots like to call this a “crag and tail formation.”

Edinburgh Castle is built on a volcanic plug or crag (A),  the Pleistocene glaciation moved from left to right (C), B is the tail of rock on the leeward side protected from massive erosion by the crag. Public Domain figure.

I saw many impressive sites on the journey and we surprised our concerned children that an 80-year-old-guy who walks with a knee brace and cane, along with a very tough spouse, were able to do a fair bit of walking in the villages and completed the steep hike up Castle Rock. There were challenges as we picked small guest houses or lodges that normally do not have elevators. The toughest was a four-story lodge in Edinburgh with narrow steps that required schlepping two, forty-pound roller bags along with backpacks up 80 steps—one at a time. The scariest time was trying to board a Birmingham train station escalator (lift was out of order), losing my balance, and falling backwards. Strange feeling looking up while in a slanted position and people screaming “shut it down”. My heavy backpack protected my head and the people behind me dodged the tumbling roller bag and held me steady until the contraption shut down. EMTs were quick to clean me up and stop the bleeding from a series of “wolverine claw marks” running up my leg (from those bitty pointy teeth on the steps). But life goes on and old geologists are tough old birds and used to tumbles. We caught a later train and had a extra ale in a nifty inn in Shrewsbury.