SILVER REEF: A STRIKE, A BOOM, THE BUST!

 Alternative Title: We’ll all be rich with the biggest silver strike this side of Hudson Bay.  Rudolph the Red-nosed reindeer (credit 1964 Videocraft International Ltd)

 

Saturday January 11, 2024. Hundreds of fishers are now crowding the back bays of the Mississippi River waiting for a sunnie or a fat perch, but most importantly the big ballgames are this weekend--The Packers and the Vikings, AKA the Pack and the Vikes, are in the NFL Payoffs. Most fishers will retreat to their tents or huts stocked with propane heaters, cold beer, chairs, color TVs, and lots of food. 

Nothing can beat the happiness of viewing a large amaryllis on a cold and cloudy January day.

I was spending the cold Wisconsin day, one only fit for ice fishers, in my cozy and warm office daydreaming while contemplating about the beautiful colors one can find in Christmas flowers. In between a snooze and a contemplation or two, I was examining some of my micro perky boxes and ran across an old box labeled BEAVERITE, WARREN LODE #5, MOHAVE CO AZ. Names like beaverite always pique my interest so I decided to explore the small sample and see what beaverite was all about! Little did I know that such exploration would lead down the proverbial rabbit hole with each side tunnel offering different confusing possibilities. For example, according to MinDat, beaverite is unknown from Warren Lode #5. More on that conundrum later. What I did find, however, was a fantastic paper by Biek and Rohrer (2006) describing the geology and mining history of a most interesting area in southwestern Utah, Silver Reef. For you see, Silver Reef in Beaver County, Utah, is the Type Locality for Beaverite, an uncommon lead iron copper sulfate: Pb(Fe³⁺₂Cu)(SO₄)₂(OH)₆.  So that serendipitous tidbit sent me sliding down the rabbit hole and finding, as Alice said—it’s rather curious you know, this sort of life.

Biek and Rohrer (2006) described the Silver Reef Mining Area as “a geologic anomaly, a historical curiosity, and an ecological novelty. It is one of the few places in the world where economic disseminated silver chloride [chlorargyrite: AgCl] was produced from sandstone."  I had the opportunity to visit Silver Reef during my late 1960s grad school days at the University of Utah, later in the 1980s while chasing fossils in southern Utah, and finally in spring 2023 during a two month, ”get out of cold weather” stint, in St. George, Utah. I tried very hard to locate a bit of the silver with each visit but no luck. Nada. However, there are many old mining structures, shafts, head frames, dump piles, equipment, a preserved original building, and a wonderful museum to keep one busy and enticed.

Stone walls remaining from a building at Silver Reef.

Some mine openings just head straight down.

Head Frame on Big Hill Reef. Photo from Reid and Rohrer, 2006.

 

Typical adit heading into the reef sandstone. Rebar gate is a recent addition to keep people out while allowing bats freedom in and out. Photo from Reid and Rohrer, 2006.

The Pine Valley Mountains form a beautiful backdrop at Silver Reef. These are some of the highest peaks in southern Utah (Signal Peak is 10,369 feet) and were formed from the Pine Valley Laccolith, perhaps the largest such igneous feature in the U.S. The quartz monzonite composing the laccolith has been dated as around 22 Ma.

Springdale Sandstone, AKA silver sandstone, exposed at Silver Reef. Public Domain Photo courtesy of arbyreed on Flicker.

The “silver history” of Silver Reef begin when a “vein of silver” was discovered in sandstone about 1866 by one John Kemple. However, poor ole John received a hearty round of laughs and guffaws since “everyone” knew silver veins occurred in “hard rocks”, usually igneous, and certainly silver was absent in most sedimentary rocks like sandstone. Ten years later a couple of Salt Lake City “bankers”, the Walker Brothers, decided to take a chance on the long-reported silver vein and sent a professional “claim guy” to stake several mining claims in the sandstone. Yep, you guessed it-----there really was disseminated silver chloride (AKA horn silver) in the sandstone and in three years over 2,000 miners were living and working on the original claims, as well as those migrating outward to dozens (hundreds) of new claims.  It turns out that not only was silver present at Silver Reef but also ores of lead, copper, and uranium. Google AI (accessed January 2025) stated, “the ore in the Silver Reef Mining District averaged 20 to 60 ounces of silver per ton.” According to MinDat (accessed January 2025) the Silver Reef District produced 7.52 million ounces of silver, 10.7 million pounds of copper, and an unknown amount of gold (probably not much). Most of this production happened during a five-year period of 1878-1882. By 1888 all the big mines had pulled up stake as the near surface ore was wiped out, the price of silver on the exchanges was heading toward the basement, and water was filling the lower tunnels. By 1903 the silver towns of Silver Reef were deserted. Sort of a typical western mining town history—a strike, the boom, and a bust!

But what about the story of silver in a sandstone? Biek and Rohrer (2006) described the Silver Reef area as one of the few places in the world where “economic disseminated silver chloride was produced from sandstone.”  A validation for ole John Kemple.

But where did the silver come from? What was the source? James and Newman (1986) suggested that “ground water leached metals from regional silver-rich rocks (presumably mostly from volcanic ash beds in the [Triassic] Chinle Formation) or from igneous systems and redeposited them in the [Jurassic] Springdale Sandstone, the first overlying permeable bed with organic material. The silver was probably transported by a sulfide-poor, chlorine-rich, brine and passed upward into anticlinal traps where it encountered reducing conditions or low-salinity groundwater that caused silver to precipitate.”

Biek and Rohrer, in their masterful 2006 article, noted that “although most workers familiar with the area agree that the Silver Reef deposits formed from metal-bearing low-temperature brines along permeable zones in the Springdale Sandstone, there is no consensus on the source of the metals, the chemistry and migration routes of ore fluids, and mechanisms to explain the variable distribution of silver, copper, and uranium.”  According to my 57-year-old class notes, that statement was about exactly what we learned in Lee Stokes’ stratigraphy classes at the University of Utah! Perhaps this is one of life’s persistent questions and I need to make a call to the Acme Building (Thanks Garrison Keilor)? You know: on the 12th Floor of the Acme Building, one man is still trying to find the answers to life’s persistent questions: Guy Noir, Private Eye.”

   Nostalgia is when you want things to stay the same!    Jeanna Moreau      

Interstate 70 bisects the San Rafael Swell and cuts through the tilted Jurassic Navajo Sandstone that is the Reef on the east side of the uplift.

In the Intermountain West one often sees the term “reef” with the most famous being the San Rafael Reef. In this usage reef does not refer to a nautical feature but to a resistant rock layer, usually indurated sandstone, that projects above its neighboring layers (often softer and easily erodible shale). At Silver Reef there are several large exposures of the resistant Springdale Sandstone (the silver bearing unit) that are exposed along, and on either side, of the nose of the Virgin Anticline, a small 30 mile long “buckle” in the rocks. The anticline is a compressional feature associated with the Lower Cretaceous Sevier Orogeny. These exposures are repeated in the rock stratigraphy due to numerous thrust faults moving the rocks around. The early silver miners thought that several different sandstone layers contained silver; however, the newly arriving geologists were able to map the faults and identify just a single silver-bearing sandstone. The resistant Springdale exposures at Silver Reef are known as the White, Buckeye, East, Big Hill, and Butte Reefs and are the major areas and mines of silver.

Notice how the reefs, outcrops of the Springdale Sandstone, are not connected but offset from each other giving the illusion that several different silver-bearing sandstone units were present. Photo from Biek and Rohrer (2006). The moral of the story—call a geologist if you locate silver!

 

Note the massive dump pile from a large mine in the reef.

Like the Phoenix, Silver Reef has experienced a rebirth, in fact, several periods of renaissance with the most successful mining activity being in 1950-1951 when 2500 pounds of uranium oxide, mostly carnotite, was hauled out for processing during the Colorado Plateau “uranium boom.” Visit Silver Reef today and you will notice a much larger rebirth as the old mines are now part of a large upscale home subdivision of Leeds and greater St George.

But wait, what about beaverite, the mineral that started this discussion? The Silver Reef beaverite, in current mineral classification, is known as beaverite-(Cu) due to copper as a major cation: Pb(Fe³⁺₂Cu)(SO₄)₂(OH)₆ and is the copper analogue of beaverite-(Zn) Pb(Fe³⁺₂Zn)(SO₄)₂(OH)₆  described from the Mikawa Mine in Japan.  It took me a long time to round up a copy of the original naming and description of the Silver Reef Type Specimen by Butler and Schaller in the 1911 American Journal of Science: check the QR code below created from https://rruff.info/Beaverite.

 

Butler and Schaller described the mineral: “Beaverite, a New Mineral. From the Horn Silver mine near the town of Frisco was collected a mineral that on examination in the laboratories of the United States Geological Survey proved to be a new species. For this mineral, which is a hydrous sulphate of copper, lead and ferric iron, the name Beaverite is proposed, after the name of the county from which it was first described. Occurrence.-The mineralization in the Horn Silver mine occurs along a fault plane that has thrown Tertiary lavas down against Cambrian-Ordovician limestone, the ore deposits being mainly a replacement of the volcanic rocks”.

 In 1992, Breidenstein and others redefined the chemistry and crystal structure of beaverite and suggested that beaverite-(Cu) is the most common of the related species with the zinc variety rare at only five different mines in Asia, Europe, and South America. In contrast, the Cu variety is uncommon but has a worldwide distribution; both are members of the Alunite Group > Alunite Supergroup.

A couple of general views of the beaverite-(Cu) specimen. FOV ~9 mm.

Note white--white cream mass, lemon yellow mass, The dark (Black) matrix is goethite. golden yellow mass, green exposures with some botryoidal, large quartz and salt and pepper scattered everywhere.

 

 

 

A golden yellow mass of submillimeter crystals of beaverite-(Cu). In fact,the mass in the middle photo is ~1 mm in width FOV. Essentially this is the limit of my photography skills.

 

Note the sub millimeter green balls of some copper mineral--malachite?, brochantite?, plumbojarosite (lead iron sulfate), osarizawaite?

Sub millimeter prismatic crystals of malachite?

MinDat noted that Beaverite-(Cu) has a yellow color that seems to range from a very pale yellow to a bright lemon yellow. However, as one peruses the photographs on MinDat and Google Photos it becomes apparent, at least to an ole plugger like me, that the mineral may also be noted in various shades of green and brown to golden brown to a golden yellow. Beaverite-(Cu) ranges from earthy masses without visible crystals (at least to me) to microcrystals often appearing as somewhat vitreous encrustations.  Whatever the case, the crystals are really tiny or almost non-visible, even with a decent, rockhound, binocular scope.

And what about the Warren Lode # 5? Not much I am afraid. Evidently it was a small claim for someone wishing for a polymetallic mine. Cannot locate any production figures. Mine not identified in Mineralogy of Arizona. No beaverite noted in MinDat; however, osarizawaite was identified (correctly?).              

To complicate identification, at least to ole plugger rockhounds, is a warning from MinDat: Beaverite-(Cu) Forms a solid solution series with its Al analogue osarizawaite .It can be distinguished from plumbojarosite  only by accurate determination of the Fe:Cu ratio. And, other Fe members of the alunite family are also visually very similar [to beaverite].  That, my fellow rockhounds is enough to scare most of us—unless we have access to nice electronic gizmos such as microprobes or XRDs!  

              

OK boys, let me tell you about the problem of identifying beaverite from the silver mines. Ole Mike just led us down a rabbit hole with that dang mineral!  Do we boot him out of the club or send him to catch the rabbit? ? Apologies to Cassius Marcellus Coolidge and his Public Domain photo.

Writing this paper was somewhat above my pay grade. One really needs an XRD or Microprobe to confirm visual identification of such small crystals. So don't quote any of my identifications as 100% accurate. As my hero Teddy Roosevelt said, Do what you can, with what you have, where you are.

 REFERENCES CITED

Bayless, P., U. Kolitsch, E.H. Nickel, and A. Pring, 2010, Alunite Supergroup: recommended nomenclature: Mineralogical Magazine, v. 74, no, 5.

Biek, Robert and C. Rohrer, 2006, Geology, mining history, and reclamation of the Silver Reef mining district, Washington County, Utah in R. Bon, R. Gloyn and G. Park (editors), Mining Districts of Utah: Utah Geological Association Publication 32.

James, L.P., and E.W. Newman,1986, Subsurface character of mineralization at Silver Reef, Utah, and a possible model for ore genesis, in Griffen, D.T., and W.R. Phillips, (editors), Thrusting and extensional structures and mineralization in the Beaver Dam Mountains, southwestern Utah: Utah Geological Association Publication 15.