TRANSCONTINENTAL RAILROAD, LUCIN, AND UTAH MINYULITE: A RARE PHOSPHATE

 

Photo taken at Promontory Summit on May 10, 1869, at the completion of the Transcontinental Railroad.

Credit Deseret News Archives.  The telegrapher sent the following message: D-O-N-E at 12:47 P.M.

I have always been interested in Utah geology since leaving South Dakota and Kansas in 1967 and heading to the University of Utah for three years of grad school.  Since rambling around the state on “field trips” was an important part of the curriculum, I became enamored with the great variety of rocks, minerals, and fossils “out there” for picking.  And picking and digging I did, but mostly for fossils.  I also found that after leaving the Wasatch Front in any direction the country was pretty wild and sparsely inhabited—perfect for a geologist and nature lover.  Over the years I walked many a mile looking for someone to help extract my vehicle or digging many hours to pile rocks under the wheels in a mud hole.  I learned early to take along plenty of water, lots of food, and extra petrol. But I, and later with my mentored students, saw some fascinating geology and noted the brightness of the stars on clear nights in the desert.

My intense interest in Utah minerals never really started until I took my leave from academe, moved to Colorado Springs, and joined the Colorado Springs Mineralogical Society.  The local mountains brought back sweet memories of hiking in the Wasatch and Uinta Mountains and I started to unpack a few boxes that held Utah “stuff.”  I was surprised at how many Utah minerals I had previously collected and stored away; it was time to sort, curate, collect, purchase, add to the collection, and write.

Darwin didn't walk around the Galapagos and come up with the theory of evolution. He was exploring, collecting, making observations. It wasn't until he got back and went through the samples that he noticed the differences among them and put them in context.        Craig Venter

One of the first specimens I nabbed in my new quest was from a rock/mineral shop in Ogden and was the green gemmy phosphate labeled variscite collected from the “Lucin Locality” in far northwestern Utah. Box Elder County, home of Lucin, is a huge hunk of land stretching from the Wasatch Front at Ogden, north along I-15 to the Idaho state line and west to the Nevada state line.  It also takes in the north half of Great Salt Lake.  The County has 5,745 square miles and outside of the small communities along the interstate is sparsely populated; the county seat Brigham City has a third of the county’s population of 57,000.  Roads are few and far between with UT 30 the only major road. 

Lucin is a well-known term in Utah due to the “Lucin Cutoff.”  The original Transcontinental Railroad ran from Ogden, in the Wasatch Front, west until toward Wendover, Nevada, on the State line but needed to detour north around Great Salt Lake. Old Lucin was a water stop for the railroad and was situated about 10 miles north of its current location.  In 1901 the railroad started construction of a trestle (~12 miles) and a causeway across the Lake and then rerouting the railroad in the general direction of Wendover.  Well, the residents of Old Lucin were about to lose their livelihood so they packed up ”lock, stock, and barrel” and moved south 10 miles to establish a new water stop at New Lucin and hence the Lucin Cutoff was in place.  The Cutoff shaved about 44 miles off the length of the railroad and also eliminated numerous curves needed to cross the Promontory Mountains. By 1959 the Central Pacific Railroad eliminated the need for a trestle and completed a causeway across the entire Lake.

In addition to the railroad, mines in the Lucin District produced, from 1870-1955, about three million dollars (year of value unknown) of low-grade copper and iron from over 6000 mines, pits, badger holes, and other miscellaneous diggings (Blue, 1960).  New Lucin is a deserted and a “Ghost Town” today.

The original route of the Transcontinental Railroad and the Lucin Cutoff.  Map Public Domain with author unknown. 

I have tromped around some of Box Elder County looking for vertebrate fossils in Miocene and Pliocene tuffaceous sediments.  I was not terribly successful but did publish on an interesting Tertiary rodent from the more eastern part of the county.  I also had the opportunity to see, in my field tripping days at the University, the Precambrian rocks in the Grouse Creek Range north of Lucin.  In those days the rocks were generally listed as older Precambrian.  Today they have more specific Archean (older) and Proterozoic (younger) ages assigned and are known as an accreted terrane, about the same age as the Wyoming Craton (>2.5 Ga), or even part of that Craton.

Location of Grouse Creek accreted terrane.  Map Public Domain and credited to: Abenne1 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

In addition, a couple of my Postings described minerals collected in the Tecoma Hills near Lucin (see Feb. 12, 2019).  However, the best- known mineral collected from Box Elder, County is the green phosphate variscite (but probably metavariscite).  It is similar looking as the variscite collected by Ed Over and Art Montgomery from the Little Green Monster Mine in Clay Canyon, Oquirrh Mountains west of Salt Lake City.  However, those Clay Canyon concretions are more colorful and contain a greater amount of crandallite (another colorful phosphate).

The Lucin phosphates were first collected and mined in the early 1900s by Frank Edison and Edward Bird on their Utahlite Hill Claim.  Since 1910 there have been a variety of rockhounds and claim owners prospecting on the Hill (mainly for variscite).  Today there is a small open pit that was previously mined but Marty and others (1999) stated “the mineral and surface rights originally belonged to the Union Pacific railroad.  Santa Fe Gold/Newmont recently acquired the mineral rights.  The property is presently under lease…”  I don’t know what has happened in the last few years since the Marty paper.

Of the minerals at Utahlite Hill, one of the more rare and most interesting is minyulite, a hydrated potassium aluminum phosphate [KAl₂(PO₄)₂(OH,F)-4H₂O].  The orthorhombic crystals are prismatic, elongated and usually terminated. Most crystals are colorless although some may exhibit shades of pale white, light green, or yellow. Crystals are tiny, usually a millimeter or two, transparent, soft (~3.5 Mohs), and often form radiating spherules or sprays. The luster ranges from vitreous to silky.

 

White sprays and spheres of silky minyulite needle-like crystals. Width of mineral mass ~2.5 mm top photomicrograph; length of middle mineral mass ~2.5 mm; width of bottom mineral mass ~6 mm.  The matrix is probably a druse of carbonate-fluoroapatite.

Marty and others (1999), in their definitive article on the Utahlite minerals, noted that minyulite crystals were limited to one small pocket and that area is now inaccessible. I have no information on the original collector of my specimen except that at one time it was in the collection of Shannon Minerals in Arizona.  Nikischer (2012) described a substantial accumulation of Lucin minyulites originally collected by Ted Morley (Piedmont Minerals). Nikischer purchased the Morely collection (early 1970s) but did not “locate” (in the several tons of mineral flats/boxes) and describe the minyulite until ~2012.  It seems these Morely Lucin specimens “may actually be the finest minyulites ever found!” However, I could not locate Lucin minyulite listed as “for sale” on the current Excalibur, or Shannon Minerals websites, nor in fact, on any dealer website.

Minyulite is a secondary mineral that needed an original phosphate mineral(s) to form.  At Lucin the secondary phosphates formed from hydrothermal solutions percolating through, and dissolving, ions in the Meade Peak Member of the Permian Phosphoria Formation. The phosphatic limestone and chert of the Phosphoria is highly brecciated and allowed fluids heated by nearby igneous intrusions to roam through the rocks and reach cooler temperatures where crystallization of the secondary phosphates occurred.  Minyulite is probably the last secondary phosphate to crystallize.  (Marty and others, 1999).

With my interest in both phosphates and the Black Hills of South Dakota it would be interesting to nab a minyulite specimen from the Ross Hannibal Mine in the Lead District.  I will keep my eyes peeled.

I want to thank Tom Loomis of Dakota Matrix for creating and encouraging my interest in the phosphate minerals of the Black Hills and other localities.

 

REFERENCES CITED

Blue, D.M., 1960, geology and ore deposits of the Lucin Mining District, Box Elder County, Utah, and Elko County, Nevada: M.S. Thesis, University of Utah.  

Marty, J., D. G. Howard, and H. Barwood, 1999, Minerals of the Utahlite Claim, Lucin, Box Elder County, Utah: Utah Geological Survey Miscellaneous Publication 99-6.

Nikischer, T., 2012, An old discovery of superb minyulite: Mineral News, vol. 28, no.4.

LUCIN UTAH