GALKHANITE: A RARE SULFOSALT FROM GETCHELL, NEVADA

Most rock and mineral shows that I attend have at least one dealer who displays colorful orange, red, yellow, and mixed-color specimens for sale. These vivid minerals often draw looks and attention and much reaching for their money stash, especially when children are asking for a purchase. Then an honest dealer will explain to the prospective buyer that the red to red-orange specimens are realgar (As₄S₄) while the orange yellow to yellow specimens are orpiment (As₂S₃); both are arsenic sulfides, and both are toxic. Therefore, care must be taken when handling these specimens, especially by children, and by adults who are not fond of scrubbing their hands after handling minerals.

Realgar (top); width ~3.0 cm., and orpiment (lower); width ~3.6 cm. from the "Getchell" Mine.

These two arsenic sulfides are always associated with each other in nature. Both have nonmetallic lusters but may have adamantine (especially realgar) to resinous lusters (especially orpiment) and are quite soft at ~1.0—2.0 (Mohs). Orpiment is photosensitive and over time will degrade into a friable, white arsenic oxide. In past centuries orpiment was used as a lemon-yellow pigment for paintings by many of the masters. However, these oxides are quite soluble in moisture of any kind and their migration to the surface on the works of art caused a color change. Today, conservators seem constantly at work trying to protect these oil paintings by limiting exposure to strong light, controlling humidity, and discontinuing the use of water-based cleaners.

Realgar, AKA ruby sulfur, almost always occurs in the same rocks as orpiment, and many times in the same individual specimen. Besides the vibrant red color, realgar differs from orpiment is that the soft mineral may be cut with a sharp knife (known as a sectile property) into thin strips and pieces. In non-crystalline specimens’ realgar may be granular or powdered or incrusting.  It burns with a blue flame and releases arsenic and sulfur fumes that smell like garlic (remember toxic). In our basic mineralogy class, we were not allowed to subject realgar to a blowpipe analysis due to the prospect of inhaling the toxic fumes. I doubt if blowpipe analyses with charcoal, along with flame tests, are even noted in a beginning mineralogy class today. It is much easier to stick samples in an electronic gizmo and receive accurate results.

Like orpiment, realgar is very photosensitive and degrades into orange yellow pararealgar (As₄S₄: same elemental composition as realgar but different internal structure), or arsenolite (arsenic trioxide As₂O₃), or orpiment.

There is a good chance that the arsenic sulfides noticed at various shows were collected at the Getchell Mine in Humbolt County, Nevada, about 35 miles northeast of Winnemucca (see Blog posting July10, 2023) on the east side of the Osgood Range. The Osgood Range is a typical Basin and Range group of mountains trending north-south defined by narrow faulted mountain ranges with adjacent rather flat basins—a horst and graben topography with normal faults. This landscape is largely due to extensional tectonics (pull-apart) of the later Tertiary (Miocene, ~17 Ma and probably continuing) after a lull in the previous extensive volcanism. However, later work by Berger and Taylor (1980) identified a much earlier (~Late Cretaceous) complex fault system on the east flank of the Osgood Mountains that was named the Getchell Fault System.

The Osgood Mountains have a thick Paleozoic section of sedimentary rocks that formed on the shallow water Continental Shelf of the North American (in current terminology) craton. However, the mountains are cored by Cretaceous igneous   plutons (notably the Osgood Mountain Granodiorite Stock) that were exposed in the horsts of the Basin and Range Orogeny. The entire section is then unconformably overlain by late Tertiary volcanic rocks (Chevillon and others, 2000). Both the Osgood Mountains Stock and the Getchell Fault System are critical to this story.

Early prospectors nosing around the Osgood Range were initially interested in copper, silver and lead associated with skarn deposits of the Osgood Stock. Instead they located skarn related tungsten and mining started in 1916 and with starts and stops lasted until the late 1950s.

However, gold was the commodity most in demand and was finally discovered ~1933 at what is now termed the Getchell Mine and brought into production in 1938. Originally gold was produced from roasted sulfide and oxide ores and the Getchell site produced nearly 800,000 ounces until production was suspended after World War II. Someone also got the bright idea to collect the arsenic produced from the roasting of the sulfides. Great idea since around 1943 U.S. government restrictions shut down many/most non-essential gold (and other) mines. However, arsenic was considered a strategic mineral and Getchell continued operation. That led to another bright idea and in 1942 Getchell increased their production of tungsten from the mineral scheelite (CaWO₄). Ones of tungsten’s major uses in WWII was the hardening of steel and it was critical for the war effort. Production dropped off after the War but continued sporadically until the late 1950s when the U.S. government terminated the “tungsten purchase program” (Defense Production Act). The production of gold after the War was off and on from both open pit and underground mines (Getchell, Turquoise Ridge, North Zone, Twin Peaks, and others) as well as heap leaching of the earlier accumulated dumps. Core drilling in the 1990s convinced mining geologists that large reserves of gold were present in the area but tied up in Carlin-type deposits (Cambrian/ ?Ordovician sedimentary rocks with sub-micron sized gold found on arsenic-rich rims of pyrite and marcasite with the richest deposits found along intersecting mid-to late Paleozoic fault zones. The sources of the gold were hydrothermal fluids associated with the Osgood Pluton and associated dikes with mineralization during two events: 1) ~83Ma [may actually be older] during emplacement of the pluton (minor event); and 2) major mineralization in the Eocene (Chevillon and others, 2000). That information was followed in 2019 by the formation of Nevada Gold Mines LLC, a joint venture by two giants of mining Carlin-type deposits: Barrick Gold Corporation (61.5% and the operator) and Newmont Corporation (38.5%). Officially the Turquoise Ridge Project but popularly known as Getchell, the complex is composed of Turquoise Ridge Underground, Vista Underground, and the Turquoise Ridged Surface mines (Turquoise Ridge Complex Technical Report NI 43-101 – March 25, 2020). I could not locate the current production figures.

MinDat listed 93 valid minerals, including one Type (getchellite, AsSbS₃), and an impressive number of commodities (gold, silver, arsenic, tungsten, antimony, mercury, barium-barite, molybdenum, fluorite, thallium, tellurium, bismuth, tin, lead, zinc, and copper) from the Getchell Complex. Besides the commodities and associated gangue minerals, the Complex is noted for the large number of colorful mercury and arsenic minerals like common arsenopyrite, cinnabar, realgar, and orpiment but also rare mercury minerals such as coloradoite (see Posting January 10, 2021), getchellite, laffittite (see Posting  February 26, 2919), and galkhaite (USGS, retrieved November 2023).

As noted earlier my interest in the Getchell centers on the arsenic and mercury minerals, and for a “long time” I wondered why these minerals crystallized at the Complex. My “knowledge” of geochemistry is a little weak, well actually quite weak, and that question really bugged me. What I do know is that hydrothermal fluids associated with the Osgood Pluton: 1) supplied the elements; 2) “As-W-Hg anomalies occur in rocks and soils over the arsenic-gold deposits and that these anomalies are not broad haloes but are restricted to the mineralized area” (Retrieved from MinDat November 2023 but original publication unknown) and 3) it has long been speculated that the origin of the many heavy metals such as Au, Hg, Sb, and Tl found in anomalous quantities in sediments in Carlin-type systems were originally derived from biogenic concentration (2011 MinDat paper authored by Phil Persson).

Submillimeter, dark cherry red cubes of galkhaite from the "Getchell Mine". 

One of the more interesting mercury minerals from the Getchell Complex is galkhaite [Hg₅Cu)CsAs₄S₁₂], a rare and complex sulfosalt (a sulfide with both metals (cesium, thallium, mercury, copper, and zinc) and semi-metals (arsenic and antimony) as cations. According to the Handbook of Mineralogy and Webmineral, it is the only known natural cesium-mercury and cesium-arsenic phase (Chen and others, 1981). Throw in the thallium and my sparse geochemical knowledge really lights up:  Cs_0.6Tl_0.4Hg_3.5Cu_1.5ZnAs_3.6Sb_0.4S_12. (Empirical formula from Webmineral). Although galkhaite was originally described from mercury deposits in Kirgizia, Russia, it is best known from the Getchell Complex and other Carlin-type rocks in Nevada.

Galkhaite, like many other mercury minerals, is red in color, usually a dark cherry red or dark orange. It belongs to the Isometric Crystal System (all three axes are equal in length and meet at right angles to each other to form a cube).  Galkhaite is soft (~3.0 Mohs) and the opaque crystals have an adamantine luster, an orange-yellow streak, and an uneven fracture. In other words, it would be easy for an ole plugger like me to confuse galkhaite with other mercury-rich minerals.

I also noted a 2011 MinDat paper authored by Phil Persson of Denver that “galkhanite is an important mineral for use in radiometric dating of Carlin-type deposits. Galkhaite is a trace mineral in at least four Carlin-type Nevada deposits and contains significant amounts of Rb and virtually no Sr, making it an ideal candidate for radiometric dating. Galkhaite from the Getchell Mine in the Potosi Mining District, Humboldt County, Nevada, was analyzed using Rb-Sr isotope dating techniques, and was found to be ~39.5 Ma [indicating the time of mineralization].”

RERENCES CITED

Burger, B.R. and B.E. Taylor, 1980, Pre-Cenozoic normal faulting in the Osgood Mountains, Humbolt County, Nevada: Geology, Vol.8, No. 12.

Chevillon, V., E. Berentsen, M. Gingrich, B. Howard, and E. Zbinden, 2000, Geologic overview of the Getchell gold geology, exploration and ore deposits, Humbolt County, Nevada: Geological Society of Nevada Symposium Geology and Ore Deposits: The Great Basin and Beyond. 

Chen T. T. , J.T. Szymanski, 1981, The structure and chemistry of galkhaite, a mercury sulfosalt containing, Cs and Tl: The Canadian Mineralogist , Vol. 19.

USGS, 2023, https://mrdate.usgs.gov/mrds/show-mrds.php?dep_id=10310336

THE 8TH ANNUAL NEW ENGLAND MINERAL CONFERENCE

 

 

 

The 8^th annual New England Mineral Conference,

Grand Summit Hotel, Newry, Maine

May 19-21, 2023

A GUEST POST BY MARK IVAN JACOBSON

 

              After a covid-imposed hiatus of four years, the New England Mineral Conference (NEMC, pronounced “Nemic’) restarted its celebration of New England minerals, and associated vocational and avocational mining and prospecting. This two-day meeting provides reports on new discoveries, updates on current mining activities, displays of some of the area’s rarest and most beautiful minerals, and a banquet announcing the Annual Mineralogical Heritage Award recognizing influential local mineral person(s).

            Details on this conference may be found on NEMC's website at  https://www.nemineral.org/.  This year's meeting, as in past years, was held at the Grand Summit Resort Hotel and Conference Center, Sunday River ski resort, Newry, Maine, on May 19-21, 2023.  Next year’s meeting will be held May 17-19, 2024. The conference is the successor to the former Maine Mineral Symposium which had been held annually for more than a decade in Augusta, Maine. With a change in leadership, led by Jeffrey Morrison, the symposium, now under a geographically broader name, restarted at an Auburn motel in 2013. After searching for a better venue, the Sunday River ski resort hotel, chosen in 2014, proved to be satisfactory with space to grow. The 2023 meeting was organized under a committee of volunteers led by President Jeffery Morrison who may be reached at nemineralpresident@gmail.com.

            The first day of this year’s meeting on Friday started with a group of short, less than 30 minutes each, talks on specific minerals from New England localities. The goal in future meetings is to continue with these short mineralogical presentations with a focus on New England and adjacent Canadian. In 2023 these short mineral talks covered the localities of Hurricane Mt., New Hampshire; Emmons pegmatite, Greenwood, Maine; Fletcher pegmatite, New Hampshire; and the Rynerson Hill pegmatite, Paris, Maine. The afternoon presentations finished with a one hour talk on critical elements mined from worldwide pegmatites by invited speaker, Philip Persson of Colorado. The critical minerals discussed focused mostly on lithium for batteries as extracted from spodumene which is a common mineral in some Maine pegmatites. Other critical minerals found in Maine include tantalum as found in tantalite and microlite, and cesium as found in pollucite. After a short break for banquet setup, attendees viewed the displays of New England minerals in the adjacent hall.   

The 2023  Annual Mineralogical Heritage Award banquet honored local field collector Cliff Trebilcock. Cliff was honored for his numerous collecting successes, especially in the Topsham Feldspar mining district. His most well-known discovery was of world class uraninite crystals from a pegmatite in the Topsham district. These specimens have set the standard for what the best crystals should look like.

Previous  Heritage  awardees have been the Perham family (Stanley, Hazel, Frank, and Jane), Terry Szenics, Raymond G. Woodman, and Irving "Dudy" and Mary Groves. Some of the best specimens of colored tourmaline, purple apatites, phosphate minerals, quartz crystals, and other rare pegmatite minerals are due to the efforts of these men and women.

Figure 1. Cliff Trebilcock (left) receiving the 2023 Mineralogical Heritage award from Don Dallaire. The award is a polished sphere of the Emmons pegmatite wall zone, Greenwood, Maine.

 Saturday had a series of morning and afternoon lectures. Don Dallaire spoke about the beryllium minerals of New Hampshire. Besides beryl, New Hampshire has produced attractive chrysoberyl, milarite, phenakite, helvite, and bertrandite. The best of these beryllium minerals were on display in the New Hampshire mineral cases organized by Don Dallaire. Jim Pecorra spoke about the discovery, mining, and reclamation of the Elizabeth Copper mine of Vermont. The Elizabeth Copper mine opened in 1809 and produced 8.5 million pounds of copper until the mine closed in 1957. Today, most of the area has been restored with some historic remains preserved in a park. Al Falster spoke on the geology and minerals of the Emmons mine, Maine. Falster, who has researched the Emmons pegmatite extensively, presented a specimen-illustrated talk on some of the rarer minerals such as lithiophilite, elbaite, and  rare element minerals such as pollucite, wodginite, cassiterite, and loellingite. Philip Persson spoke on the mineralogy and gems of the pegmatites in the Pikes Peak Batholith, Colorado. This highlighted the ever popular smoky quartz and amazonite as well as the rarer minerals such as cryolite, reibeckite, phenakite, fluocerite, and samarskite.

The day’s lectures were finished with Jeff Morrison reminiscing about mining and socializing with pegmatite miner Frank Perham, the son of Stanley Perham who mined feldspar starting in the 1920s and ran the Maine Mineral Store at Trap Corner, West Paris, beginning in 1919. Lots of free time during the day was spent visiting and buying minerals and books in the dealer’s rooms, participating in the silent mineral auction, and mingling with fellow collectors and miners.

The meetings are always followed by a one-day field trip on Sunday to nearby mines – usually a pegmatite with an opportunity to find beryl and colored tourmalines. The field trip locations offered are only revealed to attendees upon the start of the conference. This year the choices were the active Havey quarry, the Mt. Mica mine (an underground mine) with collecting allowed on the dump, and the Wheeler mica mine (quarry-tunnel numbers 1 and 2). There are many attendees who only come for the opportunity to collect. These field trips allow for collecting at famous quarries that are usually closed to all collecting. Many well-known collectors have taken advantage of this opportunity.

 

Figure 2. Fluorapatite, Waisanen Quarry, Greenwood, Maine. Mined by Frank Perham whose mined specimens were displayed in several cases to honor his memory. Perham, passed away in 2023.

 

 Figure 3. A selection of Havey mine discoveries (2013-2022) collected by Jeffrey Morrison and exhibited at the May 2023 conference..

 Figure 4. Amethyst group, Deer Hill, Stowe, Maine. Mined 1968. Cliff Trebilcock collection.

 

 Figure 4. Fred Wilda, the watercolor mineral artist, and his spouse Helen Rodak, collecting at the Havey Quarry, May 2013.

 

 Figure 5. Gary Howard (right), miner at Consolidated lower quarry (1890s Golding mine), Georgetown, Maine, May 2019. This pit produced colored tourmaline. The surrounding area during the field trip produced yellow and blue beryl, loellingite, eosphorite, and columbite.

 

 Figure 6. Joseph and his daughter, Krystalle Dorris (right side), owner-miners of the Smoky Hawk mine at Crystal Peak, Colorado, gazing at a pocket tourmaline recovered from the dump, Mt. Mica mine, Paris, May 2016.

  A conference attendee can also combine lectures, mineral purchases, and mineral collecting with a visit to the newly opened Maine Mineral and Gem Museum in Bethel. The museum is only seven miles from the conference resort. The Maine Mineral and Gem Museum is not only the premier mineral museum in Maine, it is also among the best regional museums for New England pegmatite minerals, standing as a well earned peer among the American Museum of Natural History (NYC), Harvard Museum (Cambridge), and Peabody Museum at Yale (New Haven). Although it does not contain the depth of historic specimens of these older museums, it has obtained via purchase and donation, the best suite of colored tourmalines from the famous gem mines of Mt. Mica, Dunton gem mine at Newry, Mt. Marie, Havey quarry, and Mt. Rubellite.

            The museum was created by the vision and efforts of Lawrence T. F. Stifler, Mary McFadden, and Robert Ritchie. Since the 1990s, they have worked, and guided the efforts to create this mineral and meteorite museum, and to distribute meteorites to other research institutions. The Bethel Museum also has possibly the best meteorite collection in the United States, maybe only exceeded by the American Museum of Natural History.

            The museum has also become a pegmatite research center with equipment and specimens that are available to researchers whether from other institutions or local. Circa 2010, the pegmatite research center at the University of New Orleans (MMP3), created by William Simmons, Karen Webber and Alexander Falster, moved to the museum.  With all these synergies the museum has continued to support research on Maine pegmatite minerals.

            The museum is now also the home and location for the annual pegmatite workshop, a five-day school open to public enrollment, that combines lectures on pegmatite formation and mineralogy, geared to miners, collectors and academics, with pegmatite quarry visits to observe and evaluate the lecture material.

 

Figure 7. During the Mineral Heritage Award banquet, May 2019, local collectors Bob and Pam Jackson discuss minerals with conference speaker, Bob Jones (far right) from Arizona.

.            The New England area has, since the 1990s, enjoyed a reactivation of mineral collecting, amateur prospecting and avocational mining (specimen mining by individuals as a hobby and not as their only source of income by selling specimens) in Maine, New Hampshire, Massachusetts, Connecticut, and Vermont.  Frank Perham, who just this year passed away, for many decades mentored future miners and provided advice to many mineralogists, geologists, and collectors. The generation of miners who were influenced by Frank Perham – Gary Freeman, Jeffrey Morrison, Michael O’Neal, Ron Larrivee, Jonathan Spiegel, Gary Howard, Dennis Durgin, and Paul Pinette are now actively mining in numerous areas. Due to Perham’s influence many mineral displays at the conference exhibited specimens either found by Perham or mined with him. 

 

Figure 8. John Betts, New York City mineral dealer (left) and Dennis Durgin, owner-operator of the Mt. Marie mine, comment on the Maine topazes at 2017 conference.

 

Figure 9. A portion of the Fisher quarry exhibit by miner-collector Paul Pinette in May 2023. These specimens were mined after re-opening of the quarry circa 2012.

             The New England Mineral Conference activities -the lectures, banquet, dealer mineral rooms, and silent and voice auctions provide numerous opportunities to renew and create new friendships, learn of new mineral discoveries, and collect ideas for new areas to prospect for interesting minerals. The Maine Mineral and Gem Museum provides examples of the best specimens mined in Maine and the opportunity to learn about these deposits either in the pegmatite workshop or from books sold in the museum gift shop. With all these attractions, May is a great time to meet with avid mineral collectors and view, collect, and buy minerals.

Mark Ivan Jacobson is a well-know geologist/mineralogist with a strong interest in pegmatites. He obtained a BS in mineralogy-geochemistry from Pennsylvania State University in 1973 and a MS in sedimentary geology from the University of California at Berkeley in 1976. After graduate school, he worked for Amoco and Chevron in oil and gas development as an earth scientist, completing 35 years with Chevron before retiring in 2013.

He has published numerous articles on the geology, mineralogy, and mining-collecting histories of pegmatites since 1978 as well as two major books: Guidebook to the pegmatites of Western Australia (2007) and Antero Aquamarines: Minerals from the Mount Antero - White Mountain region, Chaffee County, Colorado (1993). In addition, he has written biographies of events and persons, including “The Denver Gem & Mineral Show: A Retrospective”, and a colorful biography of early female Colorado Pegmatite Geologist, Margaret B. Fuller Boos.