The last couple of Postings have focused on minerals
containing the element vanadium.
Although many rockhounds recognize the name vanadium, that is mostly due
to the bright red, popular mineral vanadinite; most rockhounds (including me)
don’t know an awfully lot about other minerals containing vanadium. That is one reason that I have taken an
interest in the group of minerals termed the Phosphates, Arsenates and
Vanadates—trying to learn about some of the uncommon minerals.
Vanadium (V) rarely occurs in nature as a native element [it is found in fumaroles of the Colima Volcano in Mexico (Ostrooumov and
Taran, 2015)] and most vanadium-bearing
minerals are not mined specifically for the vanadium, the exception being
patronite, [vanadium sulfide, VS4] mined early in the 1900s from
Peru. However, vanadium is an important
industrial mineral used to harden steel and today is produced as a byproduct of
steel production (slag, magnetite), or from uranium mining and milling.
Although vanadium may seem to be a rare element, it is
the 20th most abundant element in rocks of the earth’s crust. Vanadium compounds occur in about 65
different minerals (Strumfels, 2019)---or take your choice---there are187 valid
species containing essential vanadium [1 element, 8 sulfides and sulfosalts, 69
oxides, 10 sulfates, 69 vanadates, and 30 silicates] (mindat.org). Vanadium has
a number of oxidation states, 3-, 1-, 1+, 2+, 3+, 4+, 5+ with the 5+ being the
most common state in minerals where it often combines with 4 oxygen ions (2- each) to form
the anion VO4 with a 3- oxidation state, the orthovanadates. However, there
are a number of other minerals where cations (metals) are combined with other
vanadium anions. And synthetically, there are a gazillion different compounds
that I don’t even pretend to try and understand.
So, in sorting out my minerals I wanted at least get a
photo of vanadium-bearing minerals in my small collection. By calling up the two web sites listed above,
MinDat and Strumfels, readers will notice the rarity and unknown names of most
listed minerals, at least they were mostly unknown to me.
Among the orthovanadates [VO4 ion with 3-
charge] I have written about pottsite (Feb. 6, 2017) (hydrated lead and bismuth vanadate [(Pb3Bi)Bi(VO4)4-H2O]), pucherite (October 15, 2019) [Bi(VO4)], vanadinite (Feb. 4, 2015) [lead chlorvanadate [Pb5(VO4)3Cl] and mentioned the
uranium mineral carnotite [K2(UO2)2(VO4)2--3H2O] several times (I shy away from uranium). But two very common orthovanadate minerals
are descloizite [PbZn(VO4)(OH)]
and mottramite [PbCu(VO4)(OH)]
I have photos of two specimens of descloizite, one
from the Whale Mine near Goodsprings, Nevada and a second from the Mammoth-St. Anthony (Tiger) Mine in Arizona.
Descloizite [PbZn(VO4)(OH)] appears in a variety of
colors, black, blackish-brown, reddish brown, and reddish orange mainly due to the
differing amounts of lead, zinc, copper and iron in the chemical makeup. The
luster ranges from vitreous to waxy and greasy but readers will often observe
the descriptive term sparkly. It is soft at ~3.0-3.5 (Mohs) and translucent to
transparent. The streak I received on a porcelain
plate is brownish red to orange.
Crystals are tough to describe on many specimens and range from “squat”
pyramidal to prismatic but then some are very tiny intergrown fibers.
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| Descloizite, Goodsprings Mining District. Width FOV 5 cm. |
Photomicrograph of submillimeter crystals from above specimen. Width FOV ~ 9 mm. Some crystals have faces while others appear as elongated ?fibers.
The Goodsprings Mining District is located near Las Vegas and the first mine was developed around 1856 by lead miners sent out by Brigham Young, the LDS President housed in Salt Lake City. There is not much information on the early history of the District; however, several small-time miners toiled to bring out a few tons of lead ore each year. Transportation of the ore to smelters was a problem and local “furnaces” had difficulties collecting high grade lead due to “contamination” by zinc. Transportation improved in 1905 when a main line of the Los Angeles-Salt Lake Railroad zoomed by a few miles from the main group of mines. Then in 1911 a branch line reached the residents and mines of Goodsprings and by 1916 around 800 hardy persons lived and worked the mines. By then zinc had become the biggest commodity but in 1915 the price of zinc started to decrease and by the end of the decade few people remained, and the largest mines had closed. However, there were small spurts of renewed mining activity during World Wars I and II with final production around mid-century. Today the Pioneer Saloon is a drawing card for tourists roaming the desert. In addition, there are still several hundred ?active claims with prospectors hoping for that pot of gold, or for any of the other previously mined commodities—silver, copper, lead, zinc, vanadium, molybdenum, cobalt, nickel, uranium, platinum or palladium. The Nevada Historical Society estimated the mines produced about 25 million dollars’ worth of metals; however, I am not certain about this figure—dollars in what year.
The Goodsprings Mining District is located near Las Vegas and the first mine was developed around 1856 by lead miners sent out by Brigham Young, the LDS President housed in Salt Lake City. There is not much information on the early history of the District; however, several small-time miners toiled to bring out a few tons of lead ore each year. Transportation of the ore to smelters was a problem and local “furnaces” had difficulties collecting high grade lead due to “contamination” by zinc. Transportation improved in 1905 when a main line of the Los Angeles-Salt Lake Railroad zoomed by a few miles from the main group of mines. Then in 1911 a branch line reached the residents and mines of Goodsprings and by 1916 around 800 hardy persons lived and worked the mines. By then zinc had become the biggest commodity but in 1915 the price of zinc started to decrease and by the end of the decade few people remained, and the largest mines had closed. However, there were small spurts of renewed mining activity during World Wars I and II with final production around mid-century. Today the Pioneer Saloon is a drawing card for tourists roaming the desert. In addition, there are still several hundred ?active claims with prospectors hoping for that pot of gold, or for any of the other previously mined commodities—silver, copper, lead, zinc, vanadium, molybdenum, cobalt, nickel, uranium, platinum or palladium. The Nevada Historical Society estimated the mines produced about 25 million dollars’ worth of metals; however, I am not certain about this figure—dollars in what year.
The Whale Mine was one of the smallest mines in the
District and the last known production of zinc (hydrozincite, hemimorphite) and
lead (wulfenite) was in 1943. These are
secondary hydrothermal minerals found in Mississippian limestone hosts.
The second specimen of descloizite in my collection
comes from the Mammoth-Saint Anthony Mine (AKA Tiger Mine), Mammoth Mining
District, Pinal County, Arizona. The
Tiger, as locals like to call it, is one of the best-known mines in Arizona and
is located about 50 miles northeast of Tucson.
MinDat noted of the 108 valid minerals that have been collected at Tiger,
10 list the mine as their type locality.
The property had both underground and surface mining but was finished by
sometime in the 1950s. A few years ago, I
visited the area and was not permitted anywhere near the past mining sites and all
structures seemed demolished and pits and shafts were filled in. What remains is a small population living in the
community of Mammoth. However, although
the mines disappeared over a half century ago, it seems quite easy to purchase
specimens from the Tiger, especially wulfenite.
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| Descloizite from Mammoth-St. Anthony Mine. Width of specimen ~2.1 cm. |
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| Photomicrograph showing crystals of descloizite from above specimen. Width of specimen ~ 1.1 cm and showing a "more true" color. |
The mines at Mammoth were polymetallic in nature and evidently metal-rich hydrothermal fluids deposited ores along fault and shear planes. Over the years the mines produced approximately 400,000 ounces of gold, 1,000,000 ounces of silver, 3,500.000 pounds of copper, 75,000,000 pounds of lead, 50,000,000 pounds of zinc, 6,000,000 pounds of molybdenum oxide, and 2,500,000 pounds of vanadium oxide (Howell, 1991).
The descloizite specimen labeled “Tiger” is a mass of
individual crystals that is vitreous to subvitreous and transparent to translucent. The best that I can describe the crystals is
compressed to squat pyramids. And, the
specimen is very difficult to photograph, at least with my equipment, due to
light reflection. The crystals really do
not look like other descloizite specimens that I have observed from Tiger but
more closely resemble groups of crystals from Namibia.
So, on the other end of the spectrum is the copper
analogue of descloizite, mottramite. But
again, some of the specimens of this mineral are tough for me to identify with certainty. The grass-green to yellow-green specimens are
certainly easier to name than the blackish-brown to black crystals. Some of these darker crystals greatly
resemble descloizite (at least to me). Mottramite is a soft mineral ~3.0-3.5
(Mohs) and has a yellowish-green streak.
Crystals range from transparent to opaque. They are less “sparkly” than descloizite crystals
and are often described as having a waxy or oily luster. Mottramite often forms
encrustations or botryoidal/mammillary masses.
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| Width FOV ~3.5 cm. |
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| Width FOV ~1.2 cm. |
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Width FOV ~7 mm.
Three photos above. Deep olive green botryoidal mass of mottramite partially covered by submillimter (really tiny) masses of black fibrous crystals of “something.” They are so small that neither my microscope nor digital camera can help me identify the buggers. However my best guess is that there are a second growth of mottramite (take a peek at photo on MinDat.org, F35-XU1 shot by Steve Rust, page 4 of the photos). |
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| Botryoidal mottramite (I think) from Glove Mine in Arizona. Something like manganese providing black covering. Width FOV ~1.1 cm. |
The specimens I have are a nifty green encrustation on shattuckite from Namibia, and botryoidal forms from Namibia and Arizona. The most attractive of these specimens is a bright green (grass green) encrustation of mottramite on a light sky blue, fibrous to spheritic mass of the rare copper silicate, shattuckite [Cu5(Si2O6)2(OH)2] from the Kandesci Mine, Kunene Region, Namibia. It seems as although the Kandesci Mine is world-famous for specimens of shattuckite, the discovery of mottramite on shattuckite is relatively new.
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| Green mottramite encrusting blue shattuckite. Width FOV ~2.5 cm. |
The Tsumeb Mine in Namibia, well known for specimens
of mottramite, is one of the most recognizable mines in Africa. MinDat states
the Mine is “renowned for a wealth of rare and unusual minerals” with 299 valid
minerals that includes the type locality of 72 minerals. It was (1907-1996) a polymetallic ore
producer but was first developed as a copper mine. The numerous rare and secondary minerals
found in the Mine are mainly due to the fact that three different oxidation
zones developed over time on/in the pipe-like ore body (Precambrian carbonates).
The minerals noted above all contain the VO4 Ion (3- oxidation state).
In my collection I found another vanadium mineral, straczekite [Ca,K,Ba)(V5+V4+)8O20-3H2O] that is chemically related to corvusite described in a previous Post (Nov. 10, 2019) since both contain V8O20 ions with a 4- oxidation state. The straczekite was picked up at a Tucson show and was collected from the Union Carbide Pit, its Type Locality in Arkansas, in an area called the Wilson Springs Vanadium Deposit (previously referred to as Potash Sulfur Springs). Hollingsworth (1967) described the geology of the vanadium deposit as being “near a contact zone between folded Paleozoic country rock and the Potash Sulfur Springs intrusive complex, in a setting that is similar to that characteristic of the Magnet Cove intrusive about six miles to the east. The vanadium constitutes about 1% of the ore, erratically disseminated in altered alkalic igneous and metamorphosed sedimentary rocks.” The Mine (four open pits) opened in 1966 and closed in 1985 producing vanadium and niobium-columbium that evidently was enriched by hydrothermal and weathering processes. Evidently all of the vanadium was produced from straczekite, hewettite [calcium vanadium oxide, V6O16)], duttonite [hydrous vanadium oxide, VO], fervanite [hydrated iron vanadium oxide, V4O16] and schoderite [aluminum phosphate vanadate]. I find it interesting that this small mine has produced: 1) 72 different minerals including three type localities: malhmoodite (hydrated iron zinc phosphate), miserite (complex hydrated potassium REE silicate), and straczekite; and 2) vanadium that was mined from very unfamiliar and somewhat rare minerals.
In my collection I found another vanadium mineral, straczekite [Ca,K,Ba)(V5+V4+)8O20-3H2O] that is chemically related to corvusite described in a previous Post (Nov. 10, 2019) since both contain V8O20 ions with a 4- oxidation state. The straczekite was picked up at a Tucson show and was collected from the Union Carbide Pit, its Type Locality in Arkansas, in an area called the Wilson Springs Vanadium Deposit (previously referred to as Potash Sulfur Springs). Hollingsworth (1967) described the geology of the vanadium deposit as being “near a contact zone between folded Paleozoic country rock and the Potash Sulfur Springs intrusive complex, in a setting that is similar to that characteristic of the Magnet Cove intrusive about six miles to the east. The vanadium constitutes about 1% of the ore, erratically disseminated in altered alkalic igneous and metamorphosed sedimentary rocks.” The Mine (four open pits) opened in 1966 and closed in 1985 producing vanadium and niobium-columbium that evidently was enriched by hydrothermal and weathering processes. Evidently all of the vanadium was produced from straczekite, hewettite [calcium vanadium oxide, V6O16)], duttonite [hydrous vanadium oxide, VO], fervanite [hydrated iron vanadium oxide, V4O16] and schoderite [aluminum phosphate vanadate]. I find it interesting that this small mine has produced: 1) 72 different minerals including three type localities: malhmoodite (hydrated iron zinc phosphate), miserite (complex hydrated potassium REE silicate), and straczekite; and 2) vanadium that was mined from very unfamiliar and somewhat rare minerals.
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| Photomicrograph of straczekite crystals. Width specimen ~8 mm. |
Photomicrograph of straczekite crystals. Width FOV ~7 mm.
Straczekite [Ca,K,Ba(V5+,V4+)8O20-3H2O, is a calcium barium potassium vanadate that occurs as a rare secondary mineral in fibrous seams in gangue at Wilson Springs and three other localities (single mines in Utah, Arizona and Germany). The crystals are dark greenish-black in color, have a greasy luster and are very soft (1-2 Mohs). They generally appear as thin laths up to 0.5 mm in length that form masses (Evans and others, 1984).
Straczekite [Ca,K,Ba(V5+,V4+)8O20-3H2O, is a calcium barium potassium vanadate that occurs as a rare secondary mineral in fibrous seams in gangue at Wilson Springs and three other localities (single mines in Utah, Arizona and Germany). The crystals are dark greenish-black in color, have a greasy luster and are very soft (1-2 Mohs). They generally appear as thin laths up to 0.5 mm in length that form masses (Evans and others, 1984).
The dark color of straczekite indicates that vanadium is
present as a mixture of valence states V4+ and V5+. During the discovery phase of straczekite
Evans and others (1984) noted that its crystal chemistry [V8O20]
seemed not to “fit” with other known vanadium minerals; however, it was
identical to a series of anhydrous synthetic layer vanadates known as vanadium bronzes.
Zhang and others (2000) believed the V8O20 layers are
composed of equal numbers of VO4 tetrahedra and VO5
pyramids connected by both corner and edge sharing. That is my limit of
knowledge of vanadium crystal chemistry.
Don’t try to digest it, I just wanted to get it down on paper as a
learning exercise to keep my brain functioning.
Another vanadium mineral I picked up in Denver is rossite, a rare
calcium vanadate tetahydrate: Ca(VO3)2-4H2O. Here the vanadium has a 5+ oxidation
state so the ion VO3 (metavanadate ion) has a 1- state. However, rossite
often/mostly dehydrates (loses water by heating) and forms the metavanadate
dihydrate, metarossite: Ca(V2O6)-2H2O where the
(V2O6) ion has an oxidation state 2-. This chemical
reaction is also reversible. It is
interesting to note that Foshag and Hess (1928), the scientists who discovered
and named these two minerals, could not identify crystal forms in rossite so they dissolved
the rossite in water, dried it to form metarossite, and then added water and
reconstituted rossite crystals. Most occurrences of these two
minerals is in carnotite (uranium ore) veins.
In describing the Colorado Plateau uranium deposits, Evans and Garrels
(1958) believed that “montroseite [(VO(OH)] is evidently the primary mineral
source of vanadium.”
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| Photomicrograph pale yellow rossite with nearly colorless metarossite. Width FOV ~1 cm. |
Rossite is a very pale yellow to white, vitreous to
pearly, transparent to to translucent, soft (2.0-3.0 Mohs) and forms “lumpy”
crusts that almost always shows some alteration to metarossite. The latter mineral is very soft at 1.0-2.0
(Mohs) and is more likely to form platy or flaky crystals. Color ranges from pale yellow to
colorless/white. Both minerals belong to
the Triclinic Crystal System. My
specimen was collected from the Sunday Mine (Sunday #2), Uravan Mining
District, San Miguel County, Colorado. Many
of the mines in the Uravan District, including the Sunday, mined ore from the Jurassic
Morrison Formation (formerly referred to as McElmo Sandstone).
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| Photomicrograph of nice crystals of metarossite covering left half. FOV ~1 cm. |
In precious posts I have written about cavansite (Feb. 24, 2016) [hydrated calcium vanadium silicate Ca(VO)(SiO4O10)-4(H2O)] and its dimorph, petagonite, the nice blue minerals rockhounds love
from the Pune District of India. Both minerals include the oxovanadium cation
VO2+ where the vanadium has a 4+ oxidation state while the single oxygen is 2-. This is one of the few vanadium
cations (positive oxidation state).
Sincosite [Ca(VO)2(PO4)2-5H2O] a
hydrous calcium vanadyl phosphate from the Black Hills
(Dec. 2, 2018) also employs the VO cation.
And finally, the other vanadium mineral in my collection
is volborthite (hydrated copper vanadate hydroxide [Cu3V2O7(OH)2—2H2O]) that uses the pyrovanadate
ion [V2O7 with an oxidation state of 4- where the
vanadium is a 5+]. The specimen was
collected from Taos County, New Mexico and described February 23, 2017. Although not in my collection, karpenkoite [Co3V2O7(OH)2—2H2O]
is the cobalt analogue of volborthite since cobalt substitutes for the copper. Martyite is the zinc analogue when zinc
replaces the copper [Zn3V2O7(OH)2—2H2O].
Engelhauptite has the water (H2O)
molecules replaced by potassium and chlorine molecules [KCu3(V2O7)(OH)2Cl].
In summary (finally), vanadium is not well recognized by most non-rockhounds
and is rarely found in nature; however, it is the 20th most common
element in rocks of the earth’s crust and is about as common as copper. The interesting “thing” about vanadium, at
least to a mineralogist, is that it forms a large community of anions
(vanadium plus oxygen) that is turn are important components of a variety of
minerals. I tried to describe some of these minerals in several postings listed above.
There is no end to education. It is not that you read
a book, pass an examination, and finish with education. The whole of life, from
the moment you are born to the moment you die, is a process of
learning. Jiddu Krishnamurti
And believe me, I have learned much about vanadium
minerals!!! WOW.
REFERENCES
CITED
Evans, H.T., Jr., R.M. Garrels, 1958, Thermodynamic
equilibria of vanadium in aqueous systems as applied to the interpretation of
the Colorado Plateau ore deposits: Geochimica et Cosmochimica Acta, v. 15, nos.
1-2.
Evans, Jr., H.T. G.N. Nord, J.M. Marinenko and C. Milton, 1984,
Straczekite, a New Calcium Barium Potassium Vanadate Mineral from Wilson
Springs, Arkansas:
Mineralogical Magazine, v. 48.
Mineralogical Magazine, v. 48.
Foshag, W.F., F. L. Hess, 1928, Rossite and
metarossite; two new vanadates from Colorado: Proceedings of the U.S. National
Museum, v.72, no. 1.
Hollingsworth, J. S.,1967, Geology of the Wilson
Springs Vanadium Deposits: Geological Society of America, Central Arkansas
Field Conference Guidebook, v. 22, no.8.
Howell, K.K., A history of the mines at Tiger, Chapter
7, 1991, In History of Mining in Arizona, Volume II, J.M. Canty and M.N.
Greeley, eds.: Mining Club of the Southwest Foundation, Tucson, Arizona.
Millman, A.P., 1960, The descloizite-mottramite series
of vanadates from Minas do Lueca, Angola:The American Mineralogist, v. 45.
Ostrooumov, M., and Y. Taran,
2015, Discovery of native vanadium, a new
mineral from the Colima Volcano, State of Colima (Mexico): Revista de la
Sociedad Española de MineralogÃa, v. 20.
D.J. Strumfels, A medley of potpourri.blogspot.com/2019/06/vanadium.html.
Zhang, L., Z. Shi, G. Yang, X. Chen, S. Feng, 2000, Hydrothermal synthesis
and crystal structure of a layered vanadium oxide with an interlayer metal
co-ordination complex: Cd[C3N2H11]2[V8O20]:
Journal of the Chemical Society, Dalton Transactions, Issue 3.