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Variscite

Last Updated: 27th Mar 2013

By Dave Crosby

At present, 24 March 2013, Mindat.org has 557 photos of variscite, a hydrated aluminum phosphate mineral (AlPO4·2H2O).
A well researched article can presently be found at: http://www.durangosilver.com/fairfieldinfo.htm "The Utah Variscite and Gem Story"
Variscite has had many names. Breithaupt in Germany first described peganite in 1830 and variscite in 1837. Peganite was later shown to be identical to variscite. The peganite was found at Striegis, near Frieberg, Saxony; the original variscite was found at Messbach, Voigtland, Saxony. The ancient name for Voightland is Variscia, named for a germanic tribe that had settled there. In 1865 variscite was rediscovered in a Celtic grave as callainite by DaMour in Lockmariaquer, Brittany. In Pontevedra, Spain, the mineral was called bolivarite. Schaller (1916) called the Lucin mineral “lucinite,” which has since been shown to be identical to variscite. Trade names under which variscite has been marketed include chlorutahlite and utahlite of Maguire (1904) and amatrice of Zalinski (1909).
Recently blue varieties have been called “variquoise.”

Variscite (AlPO4·2H20) is isostructural with strengite (FePO4·2H2O) and has a dimorphous form called meta-variscite. lt is an orthorhombic mineral and occurs as crusts, in rounded nodules, and in crystalline aggregates or in veins. The Mohs hardness is 4 to 5 and the specific gravity is 2.5. Variscite is listed as hardness 4 by Dana; some varieties may contain some minor amounts of chert or chalcedony to produce a harder material. In contrast, turquoise (CuO·3Al2O3·2P2O5·9H2O), a related mineral, has a hardness of 5 to 6 and a specific gravity ranging from 2.6 to 2.83. As a gem material, variscite is not as durable as turquoise.

The color of variscite is mostly a shade of green, although pure variscite is supposed to be white. Some of the green coloration is attributed to minute quantities of chromium. Most color descriptions include dark green, apple green, blue green, Light green, and yellow green. Many shades of variscite can be found in a single mineral specimen.

Variscite has been found or reported in other places in Utah: the Empire mine in the Lucin district, Promontory Point in Promontory district, and Utahlite Hill near Snowville - all in Box Elder County; the Golden Gate, Mercur, and Sparrowhawk mines in the Mercur district of Tooele County. In Washington County, a material similar to the Lucin variscite, which occurs as breccia fillings in white or light gray chert, is found 15 miles from St, George.
Outside the state in Esmeralda County, Nevada, variscite is found in several locations in altered rhyolite, cherty limestone, and sandy shale, where the rock is faulted and brecciated. In Arizona, variscite is found in small scattered locations.
- Hellmut H. Doelling Utah Geology, Vol.3, No.1 Spring 1976 p 13


It is a secondary mineral deposited in a near-surface environment, often containing white veins of the hydrous calcium aluminum phosphate mineral crandallite with formula:CaAl3(PO4)2(OH)5•(H2O), and sometimes blue wardite, a hydrous sodium aluminium phosphate hydroxide mineral with formula: NaAl3(PO4)2(OH)4·2(H2O). It occurs as fine-grained masses in nodules, cavity fillings, and crusts.

Appreciation of the unusual color ranges typically found in variscite have made it a popular semiprecious gemstone.

Clay Canyon Variscite - Nodules in faulted and brecciated limestones of the Pennsylvanian Oquirrh Formation
In 1893 variscite was discovered in Utah in an altered zone along a fault on the north slopes of Clay Canyon about five
miles west of Fairfield, Utah County. The deposit was claimed as a gold mine by Frank Butt and his brother. They evidently gave one of the nodules with the green mineral to F, T. Millis of Lehi, Utah, who shipped the specimen to George P. Merrill, then curator for the U. S. National Museum (Smithsonian Institution).
Packard (1894) reported on Merrill’s findings and stated that the variscite occurred as "nuggets" in a quartz vein. He described the occurrence of the variscite and Listed the deposit as the second discovered in the country. The first may have been that found in 1877 in Montgomery County, Arkansas.
In the first few years the deposit at Clay Canyon changed hands several times. The material proved to contain no gold, and it took some effort to develop a market for the green mineral. Don Maguire took over the mine and attempted to publicize the variscite as a gem material. In 1904, he reported in the Salt Lake Mining Review a siliceous vein 12 feet wide and 700 feet long. The nodules ranged in size from walnuts to coconuts. Not many nodules were found at that time. In four years only 200 carats had been produced.
An attempt by Maguire to put variscite on the American market proved unsuccessful; most of the production went to China and a little to Europe. Into the early l920’s the deposit was mined sporadically by Maguire and others as a surface mine until the "easy" material was gone. Much was sold to Ward`s Natural Science Establishment in Rochester, New York.

ln 1936 the deposit was relocated by Arthur Montgomery and Edward Over who started underground work. They were successful in striking two fresh zones of nodules, the first in 1937 and the second in 1939; the nodules were as much as eight inches in diameter. Montgomery, a geology teacher, saw to it that the nodules were preserved as mineral specimens. He donated many to the Smithsonian Institution and made others available for study of the rare phosphate minerals found with the variscite.

Esper S. Larsen, Jr., and E, S. Larsen, III, studied the mineralogy in depth and identified several new minerals.
Their work appeared in various issues of American Mineralogist (see Selected References); a partial list of the minerals includes the following: deltaite, dehmite, englishite, crandallite, variscite, gordonite, lehute, lewistonite, davidsonite, wardite, millisite, montgomeryite, overite, and sterrettite.
Since 1940 the Clay Canyon deposit has been reworked for ever-diminishing returns. Little is currently found there except for an occasional lucky find. Undoubtedly more pockets may be found in the future but not without some expense. Several tons of material have been mined over the years.
- Hellmut H. Doelling Utah Geology, Vol.3, No.1 Spring 1976 p 13


http://www.minsocam.org/MSA/collectors_corner/arc/fairfield3.htm
American Mineralogist Volume 27, pages 441-451, 1942
THE MINERALOGY AND PARAGENESIS OF THE VARISCITE NODULES FROM NEAR FAIRFIELD, UTAH. PART 3.

ESPER S. LARSEN, 3d., Harvard University, Cambridge, Mass.

TABLE OF CONTENTS. PART 3.

Origin of the variscite and later phosphates . . . . . . . . . . . . . . . . . . . . . . . .441
Character of the depositing solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Source of the phosphate material . . . . . . . . . . . .. . . . . . . . .. . . . . . . .. . . 444
Geochemistry of phosphates . . . .. . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . .445
Application of the geochemistry to the Fairfield deposit . . . . . . . . . . . . . . 446
Summary of origin . . .. .. . . . . . . . . .. . . . . . . . . . . . . . . .. . . .. .. . . . . . 449
References . . .. .. . . . . . . . . . . . . .. . . . . . . .. . . . . . . .. . . . . . . . . . . . 450
* * *
SUMMARY OF ORIGIN

Phosphorite beds at the surface were attacked by carbonated surface waters, and the resultant solutions of calcium phosphate moved downward along throughgoing channels into the zone below the water table. Here the solutions traversed aluminous material, perhaps shales, and deposited the phosphate as the aluminum salt, variscite. This reaction perhaps caused a decrease in the alkalinity of the solutions. When the phosphorite was completely removed at the surface, the downward-moving ground waters became free of phosphate material, and returned to their usual alkaline state. This return to stronger alkalinity caused a reaction with the variscite to replace it with calcium aluminum phosphate (pseudowavellite), an introduction of only calcium. Soda then became an important constituent of the solutions, perhaps derived from the weathering of shales or shaly limestones exposed at the surface; this resulted in the deposition of millisite and wardite. The soda increased the alkalinity of the solutions, eventually to the point where the deposition of wardite did not keep pace with the removal of variscite by solution. The solutions then returned to their normal alkalinity, probably with the removal of the shale and the exposure again of limestones, and again deposited pseudowavellite in place of the variscite. This ended the bulk of the mineralization. The stages following this are represented in the nodules primarily by rare crystals in the solution cavities, at first aluminum phosphates of magnesium (gordonite), followed by calcium. In the final stage aluminum is absent, and alkalies reappear. The equilibrium conditions controlling the deposition of these is not known, so that the state of the solutions forming them cannot be surmised. With the lowering of the water table below the variscite, oxidizing conditions ensued, with the deposition of abundant limonite.

It is believed that one of the major factors permitting the deposition of variscite at Fairfield, and probably some other deposits, was the existence of open fissures which permitted the surface solutions containing dissolved calcium phosphate to move rapidly downward through underlying limestone into rocks containing aluminum. In the normal course, ground waters with dissolved calcium phosphate seep down into underlying limestones, where the phosphate is leisurely precipitated by the excess of calcium carbonate. Where open channels allow more rapid descent of the solutions, the precipitating effect of the limestone is not so effective, and phosphate-bearing solutions can thus reach aluminous rocks, and the aluminum will act as the precipitant. The equilibrium conditions which determined the deposition of variscite rather than some other aluminum phosphate (such as wavellite) are not known.


Clay Canyon variscite associated minerals, information from Richard W. Thomssen of Dayton, Nevada.

http://indianvillage.com/fairfieldinfo.htm
http://www.durangosilver.com/fairfieldinfo.htm

"Species: A brief review of some of the characteristics of each mineral will be given in the approximate order in which they are believed to have formed in the deposit.

Variscite This mineral, a hydrous aluminum phosphate, occurs in dense microcrystalline nodular masses; No crystals have been found at this location. The beautiful green color has been attributed to small quantities of vanadium (0.53%) and chromium (0.069%) substituting for phosphorus (Foster and Schaller, 1966). Significant amounts of scandium, 0.001-0.1%, have been found (Frondel, Ito and Montgomery, 1968). All other phosphates in the deposit are believed to have formed at the expense of variscite through the action of hydrothermal solutions.

Crandallite The first mineral to form from variscite through the addition of calcium, this yellow to light olive green species occurs in a variety of massive and crystal habits. The most abundant forms of this mineral cover the entire spectrum from massive, cherty material through yellowish and pinkish spherulitic cleavages to white, chalky crusts. When crystallized, this mineral varies from feathery clusters of fibrous needles through more substantial, but tiny prismatic crystals to distinct flattened rhombs with an equally developed base. The Clay Canyon material was first called pseudowavellite, however, the name crandallite had priority (Palache, Berman and Frondel, 1957). This mineral in its various modes has been shown to contain significant amounts of vanadium, 0.37%, and chromium 0.67% (Foster and Schaller, 1966); strontium, >1.0% (Foster and Schaller, 1966); and scandium, 0.01-0.80% (Frondel, Ito and Montgomery, 1968). The first two elements certainly are responsible for the color.

Goyazite The existence of this mineral was obscured for many years by its resemblance to and close association with crandallite. Its strontium content was the first clue to its existence in the deposit (Frondel, Ito and Montgomery, 1968; Blount, 1974). Although tiny crystals may be present, they are impossible to distinguish from crandallite without chemical or optical tests.

Wardite The blue green to bluish grey component of the "eyes" or spherules and veining within variscite, this species also occurs in blue green to yellow crystals lining cavities in the more altered nodules (Packard, 1896; Montgomery, 1970a). (photograph and single crystal drawing) The blue green variety owes its color, no doubt, to minor amounts of vanadium and or chromium substituting for phosphorus as in the case of variscite. Solutions altering the variscite now have become enriched in sodium.

Concentric accretion of wardite and millisite.

Millisite White to clear component along with wardite of the spherules and veining noted above. No isolated crystals have been found of this species, which is similar in composition to wardite but containing calcium.

Gordonite This mineral occurs within open cavities generally near altering variscite as clusters of brilliant prismatic crystals. Crystals up to 7 mm have been reported, but they usually are in the millimeter range (Montgomery, 1970b). (photograph and single crystal drawing) Gordonite is usually colorless, but can be faintly yellow or a pleasing shade of pale violet. Here again we possibly are seeing the effects of one of the chromophores, vanadium and (or) chromium. Gordonite is the first species to appear in the deposition sequence containing magnesium and may be forming at the expense of crandallite.

Gordonite and Wardite
(photographs by Lou Perloff)

Montgomeryite
The bright blue green bladed crystals of this mineral are the most distinctive of all the well-crystallized phosphates from the Clay Canyon deposit. Crystals are in the millimeter range and typically occur in cavities implanted upon crandallite and near variscite (Larsen, 1940). (photograph and single crystal drawing)


Montgomeryite
(photographs by Lou Perloff)

Overite The rarest of the phosphate minerals, clear pale yellow clusters of tiny orthorhombic crystals of this mineral are most distinctive. (photograph and single crystal drawing) As in the case of montgomeryite, this species occurs in cavities implanted on crandallite and near variscite. These two species, like gordonite contain magnesium and probably formed at the expense of crandallite. (Larsen, 1940)


Overite on Crandallite
(photographs by Lou Perloff)

Englishite Similar to gordonite in its position within cavities close to variscite, this mineral can be readily identified by its grayish to colorless, bladed habit and, where broken, its prominent cleavage. Crystal aggregates range in size up to about 2 mm. (photograph) This is the only phosphate in which potassium is essential along with sodium and the ever-present calcium (Dunn, Rouse and Nelen, 1984, More, 1976)


Englishite on Variscite with Wardite
(photographs by Lou Perloff)

Kolbeckite This rare species was first described from Clay Canyon deposit under the name, sterrettite, as an aluminum phosphate (Larsen and Montgomery, 1940). The identity of "eggonite" from Altenberg Belgium with sterrettite was proposed while both were still considered aluminum phosphates (Bannister, 1941). Then in 1959, it was discovered that both sterrettite and kolbeckite were, in fact scandium phosphates (Mrose and Wappner, 1959). In 1980, the I.M.A. Commission on New Minerals and Mineral Names while accepting that all three minerals were identical, rejected the name sterrettite, and were almost equally divided over the name kolbeckite and eggonite. (Hey, Milton and Dwornik, 1982). Kolbeckite currently is accepted as the valid name for this hydrous scandium phosphate (Nickel and Nichols, 1991; Fleischer and Mandarino, 1991). Clear crystals of kolbeckite are generally tiny, measuring < 0.5 mm, although a few giants of 8 mm have been found. They are always on crandallite, which can be well crystallized, and are frequently associated with yellow wardite. (photograph and single crystal drawing)

Kolbeckite with Crandallite
(photographs by Lou Perloff)

Carbonate-fluorapatite Among the last minerals to form, a large variety of hexagonal crystals of this species occur in cavities generally associated with crandallite and, occasionally, with other species (Dunn, 1980). With similar habit crystals occurring in nodule after nodule, a specific difference in composition may be responsible. Perhaps it lies in differences in relative amounts of carbonate and fluorine present. Further investigation is necessary to illuminate this matter. Still enriched in calcium and phosphate, the solutions precipitating carbonate-fluorapatite no longer contain aluminum (photographs)

Carbonate-fluorapatite on Crandallite (left) and on Wardite (right)
(photographs by Lou Perloff)

Additional species Alunite, calcite and quartz together with more or less argillic limestone comprise the matrix for the phosphate nodules. Alunite is cream to white in color and moderately to coarsely crystalline. It is fairly common in the brecciated, unweathered portions of the deposit. Quartz is the dominant component in the dark-colored cherty material that is so prevalent. Limonite pseudomorphs after pyrite occur on crandallite in highly weathered nodules. This is the only evidence of the presence of sulfides having occurred in the Clay Canyon deposit, although there is locally abundant limonite-staining of the altered portions of the deposit, it cannot definitely be attributed to the weathering of pyrite."


Variscite http://www.mindat.org/min-4156.html
Carbonate-fluorapatite http://www.mindat.org/min-895.html
Crandallite http://www.mindat.org/min-1147.html
Englishite http://www.mindat.org/min-1383.html
Gordonite http://www.mindat.org/min-1728.html
Goyazite http://www.mindat.org/min-1787.html
Kolbeckite http://www.mindat.org/min-2239.html
Millsite http://www.mindat.org/min-2712.html
Montgomeryite http://www.mindat.org/min-2767.html
Overite http://www.mindat.org/min-3048.html
Stringite http://www.mindat.org/min-3801.html
Wardite http://www.mindat.org/min-4242.html

Lucin Variscite - Breccia fillings and chert replacements in the Rex Chert Member of the Permian Park City Formation
The Lucin deposit lies about five miles north of the Lucin railroad siding in western Box Elder County on a prominence known as Utahlite Hill. The hill rises 350 feet above the desert floor and is mainly an outcrop of the Rex Chert Member of the Permian Park City Formation. The first claim, for gold and copper, was located by C. J, Burke in 1902. He dug a shaft 22 feet deep and, after obtaining negative assays, abandoned it. Green oxide copper mineralization is common in the area, especially to the south in the northern Pilot Range (Copper Mountain).
The first variscite claims were located by Frank Edison in 1905, but no work was done until 1909. At that time Edison and Edward Bird, both of Montello, Nevada, began work in earnest. Sterrett (1911) of the U. S. Geological Survey, who has had one of the Clay Canyon phosphatic minerals named after him, visited the property and reported on it. Since then the property has changed hands several times and has been operated intermittently. The present owners are Dwight Bates and Leland Turner of Provo, Utah. lt is estimated that total production over the years is in the tens of thousands of pounds valued at between $50,000 and $100,000. The variscite bearing area of Utahlite Hill consists of a mineralized zone 1,000 feet in length and about 50 feet wide. The Permian Rex Chert, the host formation, is highly fractured chert with minor amounts of limestone.
Variscite occurs as breccia fillings and replacements of chert nodules. The replacements are generally eye shaped and a darker green than that found in the breccia fillings. Alteration is less pronounced than the other deposits; other minerals include metavariscite, chalcedony, limonite, and perhaps a little wardite. Since the rock is dificult to mine and shatters easily, most of th recovered pieces of variscite are small. Some of the Lucin variscite is translucent.
- Hellmut H. Doelling Utah Geology, Vol.3, No.1 Spring 1976 p 13


Amatrice Hill - Nodules in faulted and brecciated limestones of the Pennsylvanian Oquirrh Formation
Amatrice Hill, on the east flank of the Stansbury Mountains, was the last major variscite deposit to be found. Edward Bird, one of the early Lucin deposit owners, is credited with the discovery in 1905. Partners A. J. Bruno and A. O. Evans obtained control and formed the Occidental Gems Corporation. They marketed the variscite as “Amatrice,” a trade name meaning American Matrix. In 1908 Occidental reported the production of 45,000 carats of high quality variscite equal to 119.8 pounds avoirdupois. Zalinski (1911) and Sterrett (1909) are credited with first describing the property. As at Clay Canyon, production continued into the 1920's when the market diminished. The deposit was generally idle until 1944 When Dr. A. I. Inglesby, a well known collector of minerals, acquired half interest and mined a considerable quantity of variscite. After a time he thought the area to be mined out and willed his interest to Ruth Waaldo of Salt Lake City, Utah. In 1972 after nearly twenty years of inactivity the property was leased and subsequently purchased by James Atkin, and Jones of Tooele, Utah, who soon discovered a remarkable find of nodules containing several tons of material. James contacted this writer in September 1972 shortly after the new material was found, and Utah Geological and Mineral Survey Report of Investigation 74 was written (Doelling, 1973).
This new material was gathered up and described in this report. Three Queens Gem Corporation has continued to mine the deposit, but only small amounts of additional variscite have been found up to the summer of 1975.
- Hellmut H. Doelling Utah Geology, Vol.3, No.1 Spring 1976 p 14


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Comments

Thanks, Dave, for your interesting article!

The statement "Schaller (1916) called the Lucin mineral “lucinite,” which has since been shown to be identical to variscite." - reminded me of a conversation many years ago with the late Dr Gene Foord, after he had done some study on variscite from the Huanuni tin mine in Bolivia, when he referred to both "L-type" and "M-type" variscites occurring in Huanuni. I had no clue what that meant and so asked him; he said that was his shorthand for "Lucin-type" and "Messbach-type" and he believed their structures were slightly different. He passed away before publishing anything on the topic, at least as far as I'm aware.

Alfredo Petrov
25th Mar 2013 2:05pm
Alfredo, have a look at the following reference:

Salvador, P.S. and Fayos, J. (1972) Amer. Mineral., 57,
36-44.

It sounds like this terminology has been around for some time.

David Parfitt
26th Feb 2014 3:21pm

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