VANADIUM MINERALS: LASALITE AND CORVUSITE

Tell me what thy lordly name is on the Night’s Plutonian shore!” Quoth the Raven “Nevermore.”

Vanadium minerals are some sort of an enigma to most rockhounds; however, most know about a lead vanadate named vanadinite but remain rather unfamiliar with other minerals.  I would also guess that most of us have a specimen or two of vanadinite in our collections since hexagonal (barrel shape) crystals are a beautiful, bright, red color and sort of light up any mineral display.

The element vanadium (V), however, rarely occurs au naturelle and usually bonds with other elements, especially oxygen (O).  One of the common bonds is where 4 oxygen ions (each with a oxidation charge of 2 minus) combine with a single vanadium ion (oxidation charge of 5 plus) to form a vanadate ion in the form of a tetrahedron. Since the oxygen has a total of 8 minus, the oxidation charge of the vanadate ion, VO₄, is a 2 minus.  This particular ion with a negative charge always acts as an anion and commonly bonds with a positively charged metal or semi-metal (the cation).  Recently I posted a story (Oct. 15, 2019) about the mineral pucherite where the vanadate ion (anion) combines with the cation bismuth (BiVO₄).  Further back in the Blog archives is a posting (Feb. 6, 2017) on pottsite a hydrated lead bismuth vanadate [Pb₃Bi)Bi(VO₄)₄-H₂O] and vanadinite (Feb. 4, 2015) a lead chlorovanadate [Pb₅(VO₄)₃Cl].  However, vanadium also occurs in minerals where it acts as a cation with a 5 plus (usually) oxidation charge, V+++++.  One such mineral in this group is volborthite, a hydrated copper vanadium hydroxide [Cu₃V₂O₇(OH)₂—2H₂O].  My Posting on this mineral is on February 23, 2017.  All of these noted vanadium minerals are found in the oxidized zones of polymetallic mines where there is some sort of a primary vanadium source mineral.

The vanadate ion (VO₄) with a 3 minus oxidation state: 4 oxygen atoms surrounding a central vanadium atom in a tetrahedron.  Each oxygen has a 2 minus oxidation state while the vanadium is a 5 plus.  So, 8 - 5= 3 minus.  Diagram modified from Physical Geology, Opentextbc.ca.

Several decades ago I, along with my fossil collecting buddy, were out in western Colorado/eastern Utah with a group of paleontologists/geologists examining Mesozoic rocks for vertebrate fossils (yes we had permits).  On the drive back to Salt Lake City we had some time to kill and decided to check outcrops of the Jurassic Morrison Formation that were numerous south of the La Sal Mountains.  We also noticed dump piles from abandoned uranium mines scattered across the countryside that were remains of the massive Colorado Plateau uranium boom in the in the 1940s- 1960s.  I really don’t mess with uranium minerals such as carnotite (actually a uranium oxide with the vanadate ion) since I don’t want my office/collection to glow.  Generally, if a Colorado Plateau mineral is yellow or perhaps green I simply leave it alone.  However, on this trip I saw a really bright yellow substance on a pebble and picked it up to examine.  A geologist with the group told me it was a vanadium mineral rather than carnotite, so I brought it home where it resided for a number of years noted as a “vanadium mineral.”  At a later date I asked a mineralogist familiar with Plateau minerals to take a peek and his answer was lasalite, probably from the Vanadium Queen Mine—good enough for me.

As one could guess from the name, the mineral was given its moniker from the location around the massive La Sal Laccolith (see Posting Jan. 22, 2014) located south of Moab, Utah, and the high mountains that visitors to Arches National Park always notice (hey ranger, are those the Rocky Mountains?).  There are a number of named mining districts in this part of the Colorado Plateau with uranium and copper being the major metal targets (see Posting Feb. 19, 2012), and blueberry azurite being a mineral of rockhound interest (see Posting  Jan. 22, 2014).  Each of these districts has a large number of named mines, and of unnamed prospects.  The specimen I have came from one of those dumps and I will just go with the Vanadium Queen Mine. 

Lasalite is an interesting mineral for several reasons, not the least of which is the chemical formula: Na₂Mg₂(V₁₀O₂₈)—20H₂O.  Most vanadium minerals I yak about in posts are vanadates where 4 oxygen ions surround a central vanadium ion in a tetrahedron.  Lasalite starts out with 6 oxygen ions surrounding a central vanadium ion in an octahedron with edge and corner sharing of oxygen ions and ends up with a decavanadate ion (10 [deca] octahedra joined together in a single ion] with an oxidation state (charge) of 6- [let me explain that my chemistry is pretty suspect and I spent hours working on little tidbit].  In lasalite the cations are two sodium atoms (oxidation number of 1+ and two magnesium atoms (oxidation number of 2+.  So, 2 x 1=2 and 2 x 2=4 therefore 2 + 4 equals 6+, the same as the 6- in the decavanadate anion and, and therefore "everything balances balances (I am trying to "relearn" chemistry).

The decavanadate ion (V₁₀O₂₈) with a 6 minus oxidation state: 28 oxygen ions with 10 vanadium ions.  Each oxygen in a 2 minus while the vanadium is in the 5 plus oxidation state. So, 56 - 50 = 6 minus.  Diagram courtesy of Hughes and others (2005).  

Another reason for interest is that lasalite forms as an efflorescence (water in the matrix reaches the surface and evaporates leaving behind mineral residue) oxidizing on mine walls and fractures in the sandstone matrix (usually the Jurassic Morrison Sandstone in the Colorado Plateau.  The primary source of the vanadium is usually the mineral corvusite, a vanadium oxide (more later on this mineral).

In the Colorado Plateau Type deposits, a sandstone-hosted mineral deposit, vanadium minerals often occur with uranium minerals; therefore, rockhounds originally believed yellow vanadium minerals such as volborthite were radioactive; however, the Geiger Counter readings were just the radioactivity coming off accompanying uranium minerals. But, vanadium is a critical component of some uranium minerals such as carnotite: K₂(UO₂)₂(VO₄)₂--3H₂O.
 
And finally, MinDat.org notes that lasalite is identical in all respects to pascoite and other members of the Pascoite Group and can only be distinguished by X-ray diffraction or chemical methods.  Members of the Group, huemulite, hummwrite. magnesiopascoite, pascoite, rakovanite, differ in the amount of sodium, magnesium, calcium and potassium as cations combined with the V₁₀O₂₈ anion.

A yellow efflorescence of lasalite with corvusite in upper right corner.  Width FOV ~1.3 cm.

Photomicrograph showing submillineter crystal of prismatic lasalite,  Width FOV ~ 5 mm.

Lasalite has that very distinctive (like many vanadium minerals) yellow to yellow-orange color with a yellow streak.  The individual crystals are extremely small but if individuals are located they tend to be prismatic or blocky or even rounded, and glassy to silky in luster.  It is extremely soft at ~1.0 (Mohs).  Crystals are very brittle and can dehydrate to a yellow 

powder.  And, the crystals look very similar, if not identical to, other members of the Pascoite Group!

The Vanadium Queen Mine, situated on La Sal Creek Canyon, was originally staked in 1931 and went through a number of owners until being acquired by the Vanadium Queen Mining Corporation in 1955 during the “heyday” of uranium mining in the Colorado Plateau.  The ore body was a channel sandstone in the Jurassic Salt Wash Sandstone Member of the Morrison Formation.  My advisor at the University of Utah (late 1960s) once worked for the Atomic Energy Commission prospecting for uranium ore (carnotite, uraninite, tyuyamunite, metatyuyamunite, etc.) and told students that was secret for finding rich ore in the channel deposits was to locate the inside of meanders in the paleochannels.  In these inside bends plant debris carried in the stream often was deposited (trash pockets) and the carbon-rich material then provided a reducing environment for vanadium and uranium ions carried in ground water and ore bodies were created by replacement of the carbonaceous material, filling of pore spaces between sand grains, and coating of individual detridal grains.

I could not locate specific production figures for the Vanadium Queen; however, Carter and Gualtieri (1965) noted “the La Sal Creek mining district lies on the Colorado border about 30 mi southeast of Moab in San Juan County. The district is a significant V-U producer and ranks as the fourth largest V producer in Utah. Total district metal production at modern metal prices is estimated at $63 million. The major mines are the Firefly, Vanadium Queen, and Black Hat underground mines. The Vanadium Queen is one of the largest and highest grade V mines in the state at over 2% V2O5.” According to the Utah Geological Survey uranium-vanadium production in the La Sal Creek District lasted from 1904-1973 with a total dollar ore value of around 62.5 million dollars.

The source for the secondary vanadium minerals (such as lasalite ) at the Vanadium Queen Mine, and probably at many/most other Morrison Formation vanadium mines, is corvusite, a nondescript hydrated sodium, calcium, potassium, magnesium, vanadium oxide (and pretty ugly): (Na,K,Ca,Mg)₂(V⁵⁺V⁴⁺Fe²⁺)₈O₂₀--6-10H₂O. Note there are actually two

vanadium ions in the mineral, V+++++ and V++++.  In addition, the iron is ferrous iron the Fe++ oxidation state (as opposed to ferric iron, Fe+++).  

Corvusite is tough to identify except to realize that a blue-back to black to brown, opaque mineral in the sandstone matrix might be the vanadium oxide mineral (or it might be a uranium mineral!).  The specimens I have seen seem to have that distinctive blue-black color, but a color tough to pick up on my digital camera.  Most corvusite has a massive habit; however, some specimens show fibrous crystals.  All have a very dull to earthy luster and are soft at 2.5-3.0 (Mohs).

Black corvusite grains/crystals.  Width FOV, top ~6 mm, bottom ~7 mm.

The Firefly-Pigmay Mine, a uranium-vanadium deposit, is located near the Vanadium Queen Mine and has the same type of geology.  My specimen of corvusite was collected at this mine. 

The exact source of the original vanadium in these deposits is somewhat uncertain; however, Thamn, Kovschak and Adams (1981) noted the “Salt Wash deposits are essentially vanadium deposits, but as yet no convincing case has been made for the source of that vanadium. Favorite hypotheses suggest that it was (a) derived from altered llmenite and magnetite, (b) introduced diagenetically from the overlying Cretaceous sediments, or (c) was derived from the leaching and erosion of Paleozoic sediments well to the west of the Colorado Plateau. All of these hypotheses are, to some extent, plausible, but are as yet unsubstantiated.”

REFERENCES CITED

Carter, W.D., and Gualtieri, J.L., 1965, Geology and uranium deposits of the La Sal quadrangle, San Juan County, Utah, and Montrose County, Colorado: U.S. Geological Survey Professional Paper 508, 82 p., 13 plates.

Hughes, J.M., Schinder, M., Francis, C.A., 2005, The C2/m disordered structure of Pascoite, Ca₃[V₁₀O₂₈]-17H₂O): Bonding between structural units and interstitial complexes in compounds containing the [V₁₀O₂₈]₆-decavanadate polyanion: The Canadian Mineralogist, v. 43, pp. 1379-1386.

Thamm, J.K., Kovschak, A.A. Jr., and Adams, S.S., 1981, National uranium resource evaluation. Geology and recognition criteria for sandstone uranium deposits of the salt wash type, Colorado Plateau Province. Final report: United States: N. p., 1981. Web. doi:10.2172/6512174.

Several decades ago, during my halcyon days of high school, every student that went through Miss Rees' English class needed to memorize a section of Edgar Allan Poe's poem The Raven.  All any student remember a few years later was Quoth the Raven, "Nevermore."

The avian genus Corvus was named by the biologist Linneaus in his opus magnum, Systema Naturae.  Linneaus named the Common Raven Corvus corex after the Latin name for raven while the specific name, corax, is the Ancient Creek name for raven.  The American Crow is Corvus brachyrnynches with the specific name Latin for short billed. 

Having for many days past confined myself to the boat, I determined to devote this day to amuse myself on shore with my gun and view the interior of the country lying between the river and the Corvus Creek—    accordingly before sunrise I set out with six of my best hunters, ^[1] two of whom I dispatched to the lower side of Corvus creek...one of the hunters killed a bird of the Corvus genus  and order of the pica & about the size of a jack-daw with a remarkable long tale. beautifully variagated.  From the Journals of Lewis and Clark, September 17, 2004.

This is the first description of the black-billed magpie in western North America.  They named Corvus Creek for magpie, one of the few times that Lewis used a Latin zoological term.  Sometime between 1804 and the present, the name for this creek north of Chamberlain, South Dakota, emptying into the Missouri. River was changed to Crow Creek. In addition, the magpie is no longer assigned to the genus Corvus but to Pica.

Corvus the Crow is a southern constellation between Virgo and Hydra.

In 1933 Henderson and Hess named a dark colored (black or blue-black or dark brown) mineral collected from the La Sal Mining District (Jack Claim) corvusite in allusion to its blue-black color similar to the color of a raven's feathers. 


Henderson, E.P. and F.L. Hess,1933: Corvusite and rilandite. new minerals from the Utah-Colorado carnotite region: American Mineralogist, v.18.

RIFT BASINS, THAUMASITE AND LAZARD CAHN

The last Post described two minerals that had Lazard Cahn (Honorary Life President of Colorado Springs Mineralogical Society) labels accompanying the specimens.  However, I have a third Cahn specimen that lacks a label other than what is written on the outside of a small box with lid: L. Cahn, Thaumasite (white), Berger’s Quarry, Patterson, N.J.  The inside of the lid states: Thaumasite, CHY, biotite.  I am unable to interpret CHY.  The "specimen" is a residue of several hundred fragments of various minerals as noted in the microphotographs near the end of the Post. This box was gifted to me from the family of Willard Wulff, a Charter Member of CSMS and a student of Lazard Cahn. 

Burger’s Quarry (not Berger's; AKA Upper New Street Quarry) is one of several quarries near Paterson, New Jersey, that have excavated and produced “Trap Rock” for decades. Geology.com defines trap rock “as a name used in the construction industry for any dark-colored igneous rock that is used to produce crushed stone.  Basalt, gabbro, diabase, and peridotite are the most common rock types referred to as trap rock.”

The traprock exposed at Burger’s Quarry are part of several igneous formations exposed in various Mesozoic rift basins that extend from Nova Scotia, Canada to North Carolina and even further north and south in the subsurface and to the east buried by sediments of the Continental Shelf.

The Eastern North American Rift Basins along the Atlantic coast associated with the early Mesozoic breakup of the supercontinent Pangaea.  Map courtesy of  Roy Schlische and the Structural Geology and Tectonics Group at Rutgers University.

These rift basins are associated with the breakup of the supercontinent Pangaea around the Late Triassic--Early Jurassic (either side of the 200 Ma absolute age boundary) that resulted in the formation of the proto-Atlantic Ocean as the continents pulled apart.  Today we look at the Mid-Atlantic Ridge and see these same rifting processes working to further separate North America from Europe and Africa.

View of supercontinent Pangaea.  Map courtesy of Institute of Geophysics at The University of Texas Austin.

Although the Atlantic Ocean represents “full” and continuing rifting, there were several basins in North America where rifting was aborted. These basins are structurally known as half grabens.  A graben is where two normal faults bound each side of the basin—as easily noted in the Basin and Range Physiographic Province.  In a half graben there is only a single bounding normal fault. One of the best-known rift basins in the eastern U.S. is the Newark Basin located in northeastern New Jersey (and the site of Burger’s Quarry). 

Location of Newark Basin outlined in white.  The green represents Triassic and Jurassic sedimentary rocks.  The red arc in the northeast are the Wachung Mountains.  Precambrian rocks bound the western edge of the Basin.  Beyond those are the early Paleozoic rocks associated with the late Paleozoic Appalachian Orogeny.  The yellow and orange are Cenozoic Coastal Plain sediments or sedimentary rocks.  Map is Public Domain and courtesy of the U.S. Geological Survey.

Early on, as the Basin was subsiding, massive unsorted sediments from the surrounding highlands were pouring into the lowland and later consolidated to form conglomerates, sandstones and mudrocks (shale etc.) known today as the Newark Supergroup. These sedimentary rocks are usually red or orange due to the oxidation of iron oxide minerals that were in the original sediments. There are also several lacustrine formations that represent large lake systems within the Basin.

The Palisades Sill (intrusive)is along the east side of the Newark Basin and extend north along the Hudson River.  The Watchung Mountains are exposed flood basalts (extrusive) cropping out along the eastern side of the Basin.  Top map courtesy of Columbia University.  The lower drawing of the Newark Basin half graben is Public Domain and courtesy of the U.S. Geological Survey. 

The sedimentary rocks of the Newark Supergroup are well known for their enclosed fossils including dinosaurs, plants, “fish” and various invertebrates.  Perhaps the most famous tracks are those of various dinosaurs discovered in “redbeds” of the Newark.   In fact, Eubrontes, a three toed dinosaur only known from their tracks, was designated the State Fossil of Connecticut in 1991.  In the same state, Dinosaur State Park protects hundreds of tracks discovered in 1966.

Tracks named Eubrontes.  Paleontologists believe that a three-toed dinosaur created these trackways in the rift basin sedimentary rocks.  Since dinosaurs fossils cannot be positively "connected" to the tracks these impressions are termed ichnofossils. Public Domain photo courtesy of Dinosaur State Park.

The tensions associated with the pull-apart basins allowed continued faulting and tilting contemporaneous with the eruption of flood basalts and the emplacement of subsurface dikes and sills due to decompression melting of rocks of the earth’s mantle as they travel upward along thermal plumes.

Sills are igneous rocks that are sheet-like and tabular in design and intrude older rocks parallel to bedding or foliations planes (concordant).  They are usually fed by dikes, igneous structures that intrude across existing bedding planes (discordant).  Magma forming sills cools at a slower rate since the structures are intrusive into preexisting rocks.  This allows for crystals to grow larger than those associated with extrusive lava flows, usually basalt.

Cartoon showing the formation of sills that are intruded parallel to bedding plains (Palisades Sill) while dikes (dykes) intrude across bedding planes and may flow on the surface (flood basalts such as the Watchung Mountains).  Courtesy of Differencebetween.net

The best-known igneous structure associated with the basins is the Palisades Sill that trends along the Hudson River for about 50 miles north of New York City. The layered rocks form massive cliffs along the River and are a well-known landform.  The Sill is composed of diorite, a magmatic rock with larger crystals than the extrusive basalt and was the first igneous rock to appear in the Basin, perhaps around 200 Ma in the earliest Jurassic. 

Still in the early Jurassic, volcanic rocks broke to the surface in the form of eruptions and flood basalts and formed the parent rock of the Watchung Mountains in the northeastern part of New Jersey.  Olson (1980) described these episodes as three separate flood basalts that may have filled the entire basin with each eruption.  After each major volcanic episode, the basin continued sinking and was again filled with sedimentary rocks with the end result being alternating layers of basalt and red sedimentary rocks.  With aborted rifting of the basin, deposition and volcanism ceased and erosion became dominant.

Highlands of the Watchung Mountains with Paterson, New Jersey in the far background. Public Domain photo.

Today the Watchung Mountains are three (plus some smaller remnants) parallel ridges of exposed basalt that are about 400-500 feet higher than the surrounding landscape.  The First, Second and Third Watchung (as the exposures are known) are major landforms and conservation groups fight to preserve their unique plant and animal life as well as the exposures of columnar jointed traprock.

Perhaps more than any other group of minerals found in the Watchung Mountains, the best known are the zeolites (microporous aluminosilicate minerals) and their companions.  One cannot attend a rock/ mineral show without noting Watchung specimens of analcime, stilbite, apopolite, chabazite, datolite, heulandite, stilbite and especially of pectolite (sodium calcium silicate) and prehnite (calcium aluminum silicate): both silicates often appear with zeolites.  It appears that at Burger’s Quarry the extrusive magma cooled in a lake and the basalt forming pillow lava.  Many of the fine zeolite specimens crystalized in the spaces between the pillows.

The Cahn specimen in my collection, thaumasite, looks like (in my opinion) a zeolite.  However, it is a sulfate [Ca₃Si(OH)₆(CO₃)(SO₄)-12H₂O], but one that often appears with zeolites.  In the Watchungs thaumasite is formed when the basalt is heated by geothermal action.  It is usually colorless, but may be white, and forms prismatic hexagonal crystals (like apatite).  Thaumasite is quite soft (3.5 Mohs), leaves a white streak, and is translucent to transparent.  The clear, nice hexagonal crystals have a vitreous luster while the smaller fibrous crystals have a silky luster.  Thaumasite is not a common mineral and outside of the rift basin basalts is sometimes found with other calc-silicate minerals (as at Crestmore, California) or in hydrothermal copper deposits.

Photomicrographs of microcrystals of mostly transparent thaumasite mixed with biotite and others!  The longest crystal of thaumasite in the top photo (near the center) is ~ 1 mm in length.  All of the other thaumasite crystals are less than 1 mm in length.  The dark sheet mineral is evidently a  mica of the biotite family.  The greenish-brown fragments are unknown---perhaps smoky quartz sine many fragments show conchoidal fracture.   Notice the .5 mm crystal near the center of the lower photo "perched" on unknown fragments of another dark (although not shiny) mineral. Perhaps the crystal is titanite, or perhaps not.

I continue to search dusty drawers in small rock shops for additional Cahn specimens or mineral labels.  If any reader has a Cahn or Wulff label for thaumasite, please contact me.

REFERENCES CITED

Olsen, P. E., 1980, Triassic and Jurassic Formations of the Newark Basin in Manspeizer, W., ed., Field studies of New Jersey geology and guide to field trips: New York State Geological Association, 52nd Annual Meeting, Newark, New Jersey, Rutgers University.