THn AUERTcAN M rluERALocrsr
JOURNAL OF TIIE

vbl.41MINDRALOGICALSOCIETY OF ANIERICA

JULY-AUGUST, 1956

MTNERAL

Nos. 7 and 8

COMPOSTTTON OF G'UMMTTE*f

Crrllonl FnoNonr, H artard Llniaersity,Cambrid,ge,M ass.,and. U. S. GeologicalSurwy, Washington, D.C.
ABSTRACTThe name gummite has been wideiy used for more than 100 years as a generic term todesignate fine-grained yellow to orange-red alteration products of uraninite whose true
identity is unknown. A study of about 100 specimens of gummite from world-wide localities
has been made by r-ray, optical, and chemical methods. rt proved possible to identify
almost all of the specimens with already known uranium minerals.
Gummite typicalty occurs as an alteration product of uraninite crystals in pegmatite.
Such specimensshow a characteristic sequenceof alteration products: (1) A central core of
black or brownish-black uraninite. (2) A surrounding zone, yellow to orange-red, composed
chiefly of hydrated lead uranyl oxides. This zone constitutes the traditional gummite. It isprincipally composed of fourmarierite, vandendriesscheite and two unidentified phases(Mineral -4 and Mineral c). Less common constituents are clarkeite, becquerelite, curite,and schoepite. (3) An outer silicate zone. This usually is dense with a greenish-yellow colorand is composed of uranophane or beta-uranophane; it is sometimes soft and earthy witha straw-yellow to pale-brown color and is then usually composed of kasolite or an unidentified phase (Minerat B). Soddyite and sklodowskite occur rarely.
There are minor variations in the above general sequence. rt some specimens the core
may be orange-red gummite without residual uraninite or the original uraninite crystal may
be wholly converted to silicates. other specimens show clarkeite as the core, or an intermediate zone of clarkeite may form between the central uraninite and the orange-red zoneof hydrated oxides. The uranyl carbonate rutherfordine has been observed as the outermost zone in some specimens, usually more or iess admixed with uranyl silicates.
chemically the formation of the minerals of the orange-red gummite zone at the expenseof the original uraninite is characterized by oxidation of ua to u6 and hydration. There isusually little or no addition of material other than HzO at this stage, but leaching of U
relative to Pb may be a factor. The Pb in the minerals of this zone is the original radiogenic
lead of the uraninite. The outermost silicate zone is due to reaction of the hydrated oxidesof the gummite zone with meteoric or possibly hydrothermal waters carrying silica andusually also calcium. The Pb may be removed at this stage, together with uranium in part,with the formation of uranophane, beta-uranophane, or soddyite, or it may be retained inpart or entirely with the formation of Mineral B or kasolite. The Th and rare earths contained in the original uraninite usually are wholly removed during the forrnation of thesilicates.
* Contribution fromthe Department of Mineralogy and Petrography, Harvard University, No. 361; Studies on Uranium Minerals, XLt Publication authorized by the Director, U. S. Geological Survey.

539

CLIFFORD FRONDEL

540

There is also a further stage of alteration of the uraninite of pegmatites, in which thesubstance of the pseudomorphs is leached away and is either dispersed or redeposited
nearby in cracks in the matrix. The uranium minerals that occur in this way are chiefly thephosphates meta-autunite, parsonsite, and phosphuranylite, and the silicates uranophane,beta-uranophane, kasolite, and Mineral B. The alteration of uraninite in vein or other nonpegmatitic deposits follows the same general sequence of alteration described, both on ahand specimen and geologic scale. In the presence of abundant sulfides, however, a difierent
assemblage of secondary minerals is formed. This is characterized by the formation of zippeite, uranopilite, johannite, and glpsum, and there may be extensive leaching of uranium
in the ground waters.
Hrsronv

AND NoMENCLATURE

ol

GuMMrrE

Gummite is a vague term that has been and is used in various ways.
Probably its commonest present-day use is as a generic term for gumlike
or dense fine-grained pseudomorphic alteration products of uraninite
whose true identity is not known. The term ordinarily is employed inlack of any knowledge of the composition other than that uranium is amajor constituent.It alsohas beenapplied,as in the 7th edition of Dana's
System of Mineralogy, in a more restricted chemical senseto substancesthat are essentially hydrated oxides of uranium, whose true identity is
unknown, that represent the final stages of oxidation and hydration of
uraninite. George (1949) states that gummite is a generic term applied
to the usually orange or orange-yellow alteration products of uraninite
or pitchblende. Gummite is regarded by Hey (1950) as an indefinite
generic term analogous to limonite and wad.
Gummite is also loosely used without regard either to the pseudomorphic nature of the material or to its chemical composition, provided
usually that the material is orange-red to yellowish in color and dense
in appearance,and the matter thus grades into the problem of unidentified uranium minerals in general. The color of the material commonlyis orange-red, orange or yellow, but may be greenish yellow, brown, orother colors depending on the identity and, in part, the state of subdivision of the mineral or minerals present. A gumlike or resinous appearance was emphasized in the early descriptions and synonomy of thissubstance, but this feature has not been recognized as a necessarycriterion.
The name gummite has not been used always in a generic sense.The
first analyzed and clearly described gummite--the hyacinthrothesPechuran oI Freiesleben(1817) and Kersten (1332) from Johanngeorgenstadt,
so-called.in distinction from schwarzesPechuron,or pitchblende, of which
it was said to be an alteration-was said to be opaline and resembling
amber in appearance.Kersten consideredthe substance to be a distinct
4UOs'9HzO.Later, a number
species,and gave the formula as Ca3(POn)z'of more or less similar ill-defined substanceswere describedunder various

MINERALCOMPOSITION OF GUMMITE

54L

given names in the belief that they were distinct species.Some of thesesubstances appear to be essentially oxidized uraninite, others are
hydrated oxidation products thereof, and many appear to have been
mixtures with uranophane and other secondary uranium minerals. A few
of these names have found their way into the synonymy of uraninite andothers are included in the complex group of unidentified substancesnow
called gummite. The name gummite itself was first introduced by J. D.
Dana in 1868 as a speciesdesignation for an impure hydrated uraniumoxide. He included in it the material of Kersten together with the Urangummi and Uranisches Gummi-Erz of Breithaupt (1930, 1847) and the
Phosphor-Gummit of Hermann (1859).The pittinite of Hermann (1859)and eliasite of Haidinger (1852) were classedas a hydrated uranium oxide
species(eliasite) separate from both uraninite and gummite, but it was
remarked by Dana that the speciesmay not be distinct from gummite.
In 1883, Von Foullon made a detailed microscopic and chemical examination of gummite in the sense of Dana, including therein pittinite,eliasite, and the coracite of Whitney (1849) and Genth (1857), and sought
to show that the substance was a definite specieswith the composition(Pb, Ca, Ba)UsSiOrz'6HzO.Strunz Q9a9) acceptsthis view in part. He
considersthat gummite is principally a gel-like, pesudomorphousalteration product of uraninite with the formula given by Von Foullon, but
certainly also in part a mixture of different cryptocrystalline uranium
minerals. This particular matter is discussedfurther below-where it isshown from a re-examination of Von Foullon's original specimens that
his formula representsa mechanical mixture of a lead uranyl oxide witha calcium uranyl silicate.
E. S. Dana in the 1892 edition of the System oJ Mineralogy placed
gummite as a numbered speciesin the Uranate Group and stated that it
is an alteration product of uraninite of doubtful composition, with the
implication that further study would characterizeit as a distinct species.
It is difficult to seehow this could be efiected. Evidence is lacking which
permits gummite in the sense of Dana either to be identified with or
distinguished from any of the many known uranium minerals within therange of the chemical analyses and descriptions of gummite that havebeen reported, nor are type specimensavailable whose re-study would
arbitrarily resolve the problem, as the name is not based on the description of a particular specimen but was applied to a pre-existing group ofminerals thought but never shown to be identical. The present tendency
to use gummite as a generic term is a recognition of these difficulties.
Gummite together with limonite and wad are modern examplesof thegreat pocket terms that contained much of ancient mineralogy. Amongthe latter may be mentioned bole, misy, and especiallyschorl, which once

542

CLIFFORD FRONDEL

included even the rudely hexagonal columns of basaltic lava. Schorl andthe others were largely resolved into their component speciesin the decades immediately preceding and following 1800, with the advance ofchemistry and morphological crystallography in that period. fn thepresent day, gummite and its analoguesvirtually disappear as units ofdescription iI r-ray difiraction, optical, and thermal methods are applied.
The difficulties obtaining with gummite in the past were largely due tothe very fine-grained and often admixed nature of the material. It is ofinterest to note that only one mineral, uranophane, of the dozen or sothat have now been identified as constituents of gummite pseudomorphs
was known at the time of the 1892edition of Dana's SystemoJMineralogy.
In the present study, a collection of about 100 specimensof gummite
from world-wide localities was examined by r-ray, optical, and chemical
methods. All of the specimenswere partial or complete pseudomorphs
after uraninite, and had the color, denseappearance,and other characters
attributed to gummite. ft proved possible to identify almost all of thespecimenswith already known uranium minerals. Brief descriptions ofthese minerals are given in a later section of this paper. A few unidentified
minerals, apparently new species, also were found. Three of these,
Minerals A, B, and C, are briefly describedin the present report.
The optical properties of the minerals that occur in gummite or thatare associatedtherewith are summarized in Table 3, appended.The c-ray
power spacingdata for theseminerals are given in Table 4, appended.
Cunurcer, ANar-vsBsol GuuurtB
IVonexistenceoJ Gummite as a Species
The reported chemical analyses of gummite are listed in Table 1. A
brief discussionmay be given here of these analysesin advance of a detailed description of the mineralogy of the substance.Von Foullon (1883)
cited all of the older analysesgiven in Table 1. He accepted the SiOzand
CaO, both present in fairly constant amounts, as essentialconstituentsfor gummite.
and derived the formula (Pb, Ca, Ba)U3SiOrz'6HzO
The silica reported in the analysesof gummite, however, appears,fromthe observations of Genth (1879) and much other evidence, to be due toadmixture principally of uranophane or beta-uranophane,CaO'2SiOz. 2UOr.6HzO, and Von Foullon's interpretation of gummite as a definite
specieswith the formula cited never found generalacceptance.The writer
has examined all of Von Foullon's specimensthrough the courtesy of Dr.
A. Schiener, Curator of Mineralogy of the Natural History Museum,
Vienna. The North Carolina specimenshad been originally obtained by
Von Foullon from W. E. Hidden [1853-1918],an American mineralogist.
Unfortunately, it is not possible to correlate particular specimenswith

MINERAL90

COMPOSITION OF GUMMITE

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5A

CLIFPORD FRONDEL

the analyses cited by Von Foullon. X-ray and optical studies of his
specimensfrom Mitchell County, North Carolina, including the materialsof analyses I and 2 (Table 1), although these could not be specifically
identified, show that they are variable mixtures of uranophane withvandendriesscheiteor an unidentified lead uranyl oxide. Specimens ofidentical appearancefrom Mitchell County contained in other collections
also were found to be mixtures of uranophane or beta-uranophane, withvandendriesscheiteand, in some specimens,clarkeite, fourmarierite, andunidentified lead uranyl oxides. A sample of the gummite from MitchellCounty analyzed by Ross, Henderson, and Posnjak (1931), cited incolumn 4 of Table 1, and supplied for examination by Dr. George
Switzer of the U. S. National Museum, was found onfi-ray and optical
study to be an unidentified phase, Mineral C. This mineral is closely
associatedwith uranophane, and the analyzed sample is described as ofquestionable homogeneity. A new analysis of a brownish-red gummite
from Mitchell County is cited in column 12 of Table 1. This material
also gave the r-ray pattern of Mineral C.
If the analyses of the material from Mitchell County cited in columns
1,2, and 3 of Table 1 are recalculatedafter deduction of the SiOr as uranophane, CaO ' 2UOs.2SiO2.6HrO, the remaining substanceis seenfrom thedata of Table 2 to have virtually the composition of vandendriesscheite.
Analyses I and 2 have a slight excessof CaO over the requirements of
the SiOz for uranophane, and analysis 3 a slight deficiency (3.t9, 3.04,
2.05 present;2.35, 2.35,2.16 required). In the analysesas recalculated,
all of the CaO and SiOgwas deducted together with the amounts of UOrand HzO required by the SiOzpresent. The Ba present in these analyses
undoubtedly substitutes for Pb.
Analysis 11 by Kersten (1832) of the "hyacinthrothes Pechuran" from
Johanngeorgenstadtis rather similar to those just discussedif it is assumed, as was suggestedby Von Foullon (1883), that much of the Ca
reported actually is Pb. Analyses 5, 6, and 7 of eliasite and pittinite from
Joachimsthal apparently represent mixtures of limonite and uranophanewith a lead uranyl oxide. Type spbcimensof eliasite and pittinite are notavailable for examination. However, one specimenfrom Joachimsthal of
uraninite altered to orange-coloredgummite was found here to be composed of fourmarierite and uranophane and another was composed ofvandendriesscheite.Analysis 10 is closeto curite in composition. Analysis
9 was made on admittedly inhomggenous material containing perhaps
25 per cent of another mineral that appears from its description to beuranophane. The deep color and high lead content of this material suggests that the gummite component was perhaps curite. Rigal (1938)
cites a partial analysis of a very impure orange gummite from Argentina

MINEMLCOMPOSITION OF GUMMITE

545

that apparently contains about 5 per cent PbO and 80 per cent UOs'
Chaudhuri (1944) found radiometrically that an orange-yellow gummite
from Rajputana contained about 71 per cent UOs and 0.8 per cent ThOz'
Krishnan (194S) cites partial analyses of impure gummite from Rajputana. Florencio (1951) has reported an analysis of a gummite pseudomorph after uraninite from Alto do Tibiri, Paraiba, Brazrl, that apparently consistsof a hyd,rated uranyl silicate, possiblesoddyite. The analysis is reported in column 14, Table 1. Five analyses of gummite anduranium ochre from C6rdoba province, Argentina, reported by Ahlfeld
and Angelelli (1948) are cited in columns 15 to 19, Table 1. The material
Tesr-r 2, Rncer-cur-ernoAxnr,vsrs ol Guuurm

8.5

82.O
8.8

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9.6

9.14
82.00
8.86

15.31
78.51
6.18

22.10
75.52
2.38

100.0

100.0

100.0

100.00100.00100.00

BaO

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H:O

8.8

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1.5

1. Mitchell County, North Carolina. Von Foullon (1883). Analysis 1, Table 1, recalculated after deducting uranophane and Fezoa.
2. Mitchell county, North carolina. Von Foullon (1883). Analysis 2, Table 1, recalculated after deducting uranophane and FezOr.
3. Mitchell County, North Carolina. Genth (1879). Analysis 3, Table 1, recalculated
after deducting uranophane and AlzO:, PzOs.
4. Vandendriesscheite. Theoretical composition, PbO' 7UO3' 12HrO'
5. Fourmarierite Theoretical composition, PbO'4UOs 7HrO.
6. Curite. Theoretical composition, 3PbO 8UOr 4HzO.

occurs as alteration products of uraninite in pegmatites. The analyses
resemble those of gummite in general, and apparently are mixtures withuranophane and, in analysis 19, possibly also quartz or other insoluble
material. The presenceof uranophane (?) is noted in material from Angel
mine (analysis 16, which lacks CaO), and this mineral was identified in
specimensof gummite from C6rdoba examined by the writer'
The r-ray and chemical evidence indicates that the gummite from
Mitchell County, North Carolina, is not a definite compound containing
essential Ca and Si, as was believed by Von Foullon, but is a mixture ofa calcium uranyl silicate, uranophane, with a lead uranyl oxide, usually
vandendriesscheite. This view is strongly supported by the fact thatsimilar specimensof gummite, from localities over the world, are foundto be composed of lead uranyl oxides, usually vandendriesscheite,

546

CLIFFORD FRONDEL

Mineral ,4, Mineral C, or fourmarierite, admixed or associatedwith thesilicates uranophane, beta-uranophane,kasolite, or Mineral B.
Srqrroxrrar Ar,mnatron or, UnlNrNttn
Mineralogy
Gummite pseudomorphs after uraninite crystals show a very characteristic sequenceof alteration products that has long been recognized.
Brief descriptions have been given by Kerr (1877), Genth (1879), Hidden(1881), Von Foullon (1383), Hofiman (1901), Tipper (tg9), Schoep(1921), Buttgenbach (1922), Hacquaert (1927), Ellsworth (1930), Ross,
Henderson,and Posnj,ak(1931), Yagoda (t946), Sarkar and Sen (1946),
Krishnan (1948), Bakken, Gleditsch, and pappas (1948), and page(1950). The best examplesare afforded by the uraninite crystals found inpegmatites, but the same principles apply to uraninite in all of its occurrences.when a typical, partly altered crystal is broken across,one finds:(1) A veined or embayed central core of uraninite. The color may be
black or, in relatively highly oxidized material, greenish black, brownish
black, or dark brown. (2) A surrounding zone of orange-red, orange,
brownish-red, brown, or yellow material that constitutes the traditional
gummite' This material is dense in structure, although microscopically
crystalline, and ranges from vitreous or gumlike to dull and earthy inappearance.In composition it consistschiefly of hydrated uranyl oxides,
often containing considerable amounts of essential lead together withminor amounts of calcium and barium. The commonest mineral constituents are vandendriesscheite,fourmarierite, Mineral A, and.Mineral
C. Curite, becquereiite, and schoepite also have been identified, andseveral unidentified minerals have been found. (3) An outer zone of
uranyl silicates. This zone generally is hard, dense,and microcrystalline
with a greenish-yellow color and vitreous luster but may be soft andearthy with a straw-yellow color and dull luster. The hard, vitreousmaterial often faithfully preservesthe minute surface details of the original uraninite crystals. The silicate zone grades into the hydrated oxidezone and has been derived from it. The principal minerals of this zone
are uianophane, beta-uranophane, and kasolite. Mineral B, soddyite,
sklodowskite, and several unidentified minerals also occur.
This sequence may vary considerably in detail. Thus, the original
uraninite may be completely oxidized leaving a pseudomorph of orange
gummite, with a more or less thick rind of uranium silicate, or thepseudomorph may consist largely or entirely of uranium silicate. Further,
additional more or less well marked zones may be present. Specimensfrom a few localities were found to have an irregular outer zone of theuranyl carbonate rutherfordine which graded inwardly into oranse-red

MINERALCOMPOSITION OF GUMMITE

547

gummite. Complete pseudomorphs of rutherfordine also were observed.
Other specimensshowed brown clarkeite as the core, or an intermediatezone of clarkeite was present between the uraninite core and the outergummite and silicate zones. The gummite zone itself may be irregularly
mottled or veined in orange-red, red, or yellow colors due to admixtureof various minerals.
There is also a further stage of alteration of the uraninite of pegmatites,in which the substanceof the pseudomorphs is leached away and is dispersed or redepositedin cracks in the matrix in the immediate neighborhood of the pseudomorphs.The secondary uranium minerals that occur
in this way are chiefly the phosphates meta-autunite, parsonsite, andphosphuranylite and the silicatesuranophane, beta-uranophane,kasolite,
and Mineral B.
The alteration sequencejust described seems to take place at essentially atmospheric conditions through the agency of meteoric waters. It
also has been considered, apparently first by Ross, Henderson, andPosnjak (1931), that the alteration of the uraninite of pegmatites togummite and silicates took place during the late hydrothermal stageof
pegmatite formation. It may be noted in this connection, however, thatthe uraninite of various nonpegmatitic deposits, including the Colorado
Plateau region, Katanga, Great Bear Lake, and Joachimsthal, undergoes
an identical sequenceof alterations under what are clearly weathering
conditions. George (1949) also points out that in the uraninite vein deposits of Portugal, uranophane and beta-uranophane are much moreabundant toward the surfaceand are there associatedwith typical supergene uranium minerals such as autunite and torbernite. According to
Websky (1853, 1859), uranophane at its type locality, Kupferberg,
Silesia, is formed by atmospheric influences on primary uraninite in thecopper veins. Hayden (1914) remarks that uranium ocher (gummite) is
common at the surface of pegmatites in the Gaya district, India, andpassesinto pure uraninite in depth (where a nodule 36.pounds in weight
was found). This also is true in the New England pegmatites. The occurrence of uraninite in pegmatites has been discussedby Page (1950) andQuensel (1940). Lang (1952) mentions 27 occurrencesof gummite in
Canada, mostly in pegmatites.
The sequence of alteration of uraninite on a single-crystal scale isbroadly paralleled by the alteration of vein deposits of uraninite on a geologic scale. Thus, in the Katanga deposits the uraninite alters first to
hydrated uranyl oxides or lead uranyl oxides, principally becquerelite,
schoepite, vandendriesscheite,and fourmarierite. These minerals occur
chiefly as crystalline crusts and masses,involving deposition from solution, and are not pseudomorphous alteration products. Pseudomorphs

s48

CLIFFORD FRONDEL

also occur but are rare. The very rare secondary mineral ianthinite, ahydrated oxide of quadrivalent uranium, is formed earlier than thesesexivalent oxides and occurs as crystals in veinlets penetrating uraninite.
The formation of the hydrated uranyl oxidesis accompaniedand followedby the deposition of hydrated uranyl phosphates and silicates, generally
containing copper, calcium, magnesium, or lead in addition to uranium.
These have formed as crusts and masseschiefly by the action of meteoric
waters carrying Cu, Ca, Mg, phosphate, and silica on the earlier formed
hydrated oxides. The phosphate apparently has been derived by meteoric
waters from the country rock. Unfortunately there is no detailed accountof the paragenesisof the secondary uranium ntinerals at Katanga in theavailable literature. Brief accounts are given by Robert (1940), Katz andRabinowitch (1951), Everhart (1951), Thoreau and Terdonck (1933,
1935), Bain (1950), and Kohl (1954), and scatteredremarks are foundin the literature descriptive of individual species.The above sequence,
recognizedin the literature, is confirmed by the examination of Museum
specimens.Uraninite deposits rich in sulfides generally alter directly tothe sulfates zippeite, uranopilite, and johannite, and probably much of
the uranium is lost in the meteoric circulation if the water is acid. The
uraninite deposits of the Canadian shield, as a Great Bear Lake and Lake
Athabaska, show only. a very slight supergene alteration, chiefly tohydrated uranyl oxides and silicates.
' The uraninite of the sandstone-type deposits of the Colorado Plateau
generally is intimately associated with montroseite and other primary
low-valence vanadium r-nineralsand on oxidation passes to carnotite,tyuyamunite or other secondary uranyl vanadates. In a few instances,
however, as at the Monument No. 2 mine, Monument Valley, Arizona,and the Delta mine, San Rafael Swell, Utah, uraninite is found surficially altered to becquerelite and schoepite; the lead-bearing oxides
fourmarierite and vandendriesscheiteare lacking except in traces. Leadbearing secondaryuranium minerals, including kasolite, curite, parsonsite, dewindtite, renardite and dumontite, are lacking in general in the
Plateau deposits,in contrast to their abundant occurrencein the Belgian
Congo. This is owing to the general absenceof lead-containing mineralssuch as galena in the unoxidized ores and to the low content of radiogeneic lead in the uraninite of the Plateau deposits.
Chemistry
The chemistry of the sequential alteration of uraninite crystals ofiers
a number of interesting problems. In the initial stage of alteration, theuraninite itself oxidizes over a range of composition without destructionof its crystal structure. In this, it is well established that valence com-

MINEMLCOMPOSITION OF GUMMITE

pensation for the serial oxidation of U4 to UG is effected by a coupled
entrance of oxygen into the vacant eight-,coordinatedpositions of thestructure. The extent of oxidation that is possible before the structure
breaks down is not known. It appears to be in the neighborhood of UOz.s(see Katz and Rabinowitch, 1951) or UOz.o(see Brooker and Nuffield,
1952).The efiect that the presenceof Pb, Th, and rare earthsin substitution for U has on the extent of the oxidation is not known. A similar
mechanism of compositional variation is known in other substancesisostructural with UOz, including the substitution of Y, Th, or Ua for Ca
in CaFz; La for Sr in SrF2; and Bi for Pb in PbFz. In these instances F
enters the interstitial positions to effect valence compensation. It also
has been suggestedthat the content of U6 in natural uraninite is due to an
auto-oxidation involving radioactive decay processesindependent of theenvironment (Ellsworth, 1925, and Khlopin, 1938). Attempts based on
this assumption to use the TJ4/rJ6ratio for age calculations have been
unsatisfactory. It seemslikely that the oxidation is a forerunner of thehydration and chemical reaction with traversing, oxidizing solutions that
ultimately convert the uraninite completely into the minerals of thegummite and silicate zones.It is of interest to note that neither UeOsnor
the tetragonal polymorph of partly oxidized uraninite (-UOz.a) havebeen found in nature, although both are stable, well-known compounds
easily formed by the oxidation of UOr.
In the second stage of alteration, the uraninite is destroyed and its
constituents are reorganizedinto the hydrated lead uranyl oxide mineralsof the orange-redgu'mmite zone.The changeinvolves complete oxidationof the uranium to U6 and hydration, without significant gain of material
other than water, but possibly with leaching of uranium in part relative
to lead. It is apparent from the examination of many specimensthat theparent uraninite does not have to be oxidized to its limiting content of
U6 in the UOr structure-type before it converts to these new phases,
although it may alter more readily if it is relatively highly oxidized. The
radiogenic lead of the original uraninite seemsto be wholly retained in
the new minerals formed at this stage.The particular minelal or minerals
formed here, whether schoepiteor becquerelite(little or no lead), vandendriesscheite(9.1 per cent lead), fourmarierite (15.3 per cent lead), er
curite (22.1 per cent lead) presumably reflects the amount of radiogeni.c.
lead available in the original uraninite. Leaching of uranium relative t6
lead is an added faclor. No zoning of the minerals of this stage in pointof lead content has been observed. The amount of radiogenic lead inuraninite ordinarily runs from about 3 to 10 weight per cent PbO, but asmuch as 19 per cent PbO has been reported. Curite, with the highest content of Pb of the secondary hydrated uranyl oxides, is very rare in gum-550

CLIFFORD FRONDEL

mite alteration pseudomorphs. Schoepite and becquerelite, with little or
no lead, also are very rare. At Katanga, its principal locality, curite isformed chiefly by direct crystallization from lead-containing solutions
and is relatively late-formed in the paragenesis. The question of thevalence state of the Pb present in uraninite and in some of the redcolored secondary oxides requires further investigation. ft always is reported as Pb2 by analysts. Wasserstein (1954), in his work on the determination of age by unit-cell measurementsof uraninite, assumesthe lead
to be present as Pba.
In the third stage of alteration, the hydrated oxides of the gummite
zone react chemically with traversing solutions, ordinarily of the meteoric
circulation but possibly at times of hydrothermal origin, with the formation of uranyl silicates and, occasionally,of the uranyl carbonate rutherfordine. Calcium ordinarily is added at this time, in addition to silica andwater, giving rise to the characteristic minerals of this zone, uranophane,beta-uranophane, and Mineral B. Soddyite, a uranyl silicate lacking Pb,
Ca, or other cations, also may form at this stage but is rare. Lead, retained during the gummite stage, ordinarily is completely lost during theformation of the silicates. Sometimes it is retained and concentrated
relative to uranium with the formation of kasolite, with 37.5 per centPbO, and Pb also is sometimes present in solid solution in Mineral ,8.
Uranium, present in the silicates of this stage in amounts between 49
and 67 per cent UO3, apparently must be lost in part since the alterationcommonly takes place without appreciable change in volume (pseudomorphic).
The history of the thorium and the rare earths contained in the original uraninite is not entirely clear. Analyses 4, 9, 12, and 15 to 19 ofTable 1 indicate that these elements are retained at least in part in theminerals of the gummite zone.This also is indicated by a spectrographic
study of zoned pseudomorphsmade for the writer by Mr. H. C. Harrison.
This study further showed that the thorium and rare earths tend to be
Ieachedout during the silicate stage of alteration. An analysis of uranophane cited beyond, however, indicates that thorium and rare earths may
be retained in small part in the silicate stage, but these elements are notfound in most analysesof uranophane and beta-uranophane.The studies
made of changesin the ratios of uranium, thorium, and lead during theoxidation of uraninite, in connection with the determination of geologic
age by the U, Th/Pb method, indicate that thorium tends to decrease
and lead to increase relative to uranium as alteration proceeds. [SeeBakken, Gleditsch, and Pappas (1948), Gteditsch and Bakken (1937),
Bakken and Gleditsch (193S),Alter and Kipp (1937),Hecht (1931),andHecht and Kroupa (1936).] These observations apply to uraninite in theMINEMLCOMPOSITION OF GUMMITE

551

initial stages of alteration. Uraninite that has passed into the gummite
stage of alteration is worthless for age determination work. Flyn (1937)
has described experiments on the leaching of uraninite in water in closed
tubes at 190' C. Yagoda (1945) describesthe occurrence of radiocolloid
aggregates in gummite and gives a color photograph of a gummite
specimen. The radiocolloids apparently owe their origin to the leaching
and local reprecipitation of radiogenic radium as radium sulfate, which
has since largely decayed to Pb206SOn.
Clarkeite contains sodium and calcium as essential constituents, together with lead, and occurs in the inner part of some uraninite pseudomorphs in pegmatites. The writer inclines to the view of Ross, Ilenderson,
and Posnjak (1931) that the clarkeite was formed by reaction of theuraninite with late pegmatitic hydrothermal solutions containing alkalies.
The outer gummite and silicate zones of these pseudomorphs probably
were formed much later by meteoric solutions.
Drscnrprrow or Mrvsnar.s PRISENTrN GuMMrrE
Becquerelite,
TUOB'11HrO (?)
Becquerelite was not identified as a constituent of the gummite specimens examined in the present study. It has been reported by Steinkuhler(1923) and Hacquaert (1927) in uraninite pseudomorphsfrom Katanga.
The mineral ordinarily occurs at this locality not as an alteration
product but as drusy crusts and aggregates that have been deposited
directly from solution in the supergenezone. It was observed as a direct
alteration product of massive uraninite, however, in specimensfrom theMonument No. 2 mine, Apache County, Arizona, the Delta mine, San
Rafael Swell, Utah, and Lake Athabaska, Canada. The rarity of
becquerelite in gummite is rather surprising, especially since the mineralapparently can contain lead in solid solution. Schoep (1936) describes
specimens from Katanga showing a central core of uraninite that hasaltered first to becquerelite and orange fourmarierite and later to green
vandenbrandeite and cuprosklodowskite. Scheerer (1847) described auraninite crystal from a pegmatite in Norway that had been altered toa pale yellow hydrated uranyl oxide, possibly becquerelite or schoepite.
B eta-uranophane,Ca(UOtr(SiOtr(OH)2' 5HrO
Beta-uranophane, the monoclinic pqlymorph of tlranophane, wasfound in a few occurrencesas the chief constituent of the outer, silicate
zone of alteration. fn these occurrencesthe mineral is identical in colorand general appearance with uranqphane (which see); it is best distinguished by optical and *-ray tests. Beta-uranophane has inclined extinction and relatively high indices of refraction (Table 3). Steinocher and552

CLIFFORD FRONDEL

Nov6dek (1939) note that beta-uranophane may convert to uranophane
when finely crushed, so that care must be taken in preparing samplesfor
rc-ray or optical study. fn gummite pseudomorphs, beta-uranophane
characteristically has a yellowish-green color sometimes inclining tolemon yellow. Dense material is slightly translucent and has a weak
vitreous to waxy-vitreous luster. Like uranophane, the mineral also
occurs as soft, rather porous aggregatesof a dull or earthy luster and theninclines to straw yellow and brownish-yellow shades of color. This soft
material seemsto be a product of leaching of the dense,vitreous pseudomorphs. Under the microscope the mineral appears as matted aggregates of fi.bers,often minute in size and distorted, and accurate opticalmeasurementsare difficult to obtain. Beta-uranophane was identified inmaterial from the following localities: various pegmatites in the Spruce
Pine district, Mitchell County, North Carolina; Newry, Maine; theRuggles pegmatite, Grafton Center, and the Palermo pegmatite, North
Groton, New Hampshire; Easton, Pennsylvania; Rajputana, India. It
was also found as crusts of acicular crystals associated with alteringuraninite at Theano Point, Lake Superior, Canada, and Wblsendorf,
Bavaria.
(Na, Ca, Pb, H2O)2U2(O,Clarhei,te,
HrO)t
Clarkeite was identified in a number of specimens from the Spruce
Pine pegmatite district, North Carolina-the type locality for themineral. It also was found at a new locality, the Ajmer district, Rajputana, India. The composition and properties of clarkeite have been
recently described by Gruner (1954) and by Frondel and Meyrowitz(1956). Clarkeite occurs as a direct alteration of uraninite. It is earlier
formed than the minerals of the orange-red gummite zone and may alter
to them. It difiers from these minerals in its dark-brown or mahoganybrown color, and in containing Na and Ca in addition to Pb. It occurs as
dense, fine-grained aggregates.The indices of refraction are high, nearthose of curite, and vary considerably with variation in the ratio of Na,
Ca, and Pb (Table 3). A positive identification is best made by r-ray
means (Table 4). The mineral also resemblesthe brownish-black, relatively highly oxidized types of uraninite. Clarkeite has been said to occur
in reddish-brown gummite at the Ruggles pegmatite, Grafton Center,
New Hampshire, but it was not observed in specimensfrom this locality
examined in the present study.
Curite, 3PbO 8UOB HrO(?)
Curite was not identihed with certainty in any of the gummite pseudomorphs here examined. It may have been admixed in very small amounts

MINERALCOMPOSITION OF GUMMITE

JJJ

in some of the fourmarierite pseudomorphs. In one instance an tc-ray
pattern very close to that of curite was obtained from a deep orange-red
gummite from Mitchell County, North Carolina, but the indices of refraction were much too low to confirm the identification. The orangered to red color of many gummite specimensis not due to curite, as has
been suspectedin the past, but chiefly to fourmarierite and in part tovandendriesscheite.Curite pseudomorphs after uraninite crystals from
Katanga have been described by Vernadsky and Chamie (1924), Yan
Aubel (1927), Schoep (1930), and Hacquaert (1927). Schoep and
De Leenheer (1937) found that certain colloform crusts from Katanga,termed gummite by them, were composed of curite (analysis 10, Table1). Their belief that all gummite is composed of curite is incorrect. A
transparent, isotropic substancewith a bright-scarlet color found here as
an alteration product of uraninite from Fone, Gjerstad, Norway, may be
an amorphous gel form of curite. It has an index of refraction slightly
over 2, and did no'! give an n-ray difiraction pattern. A flame-scarlet
alteration product of uraninite from Villeneuve, Quebec, analyzed by
Ellsworth (1930) and cited in Table 1, might contain curite.
Fourrnarierite,PbO' 4UOa'THIO (?)
Chemically, it is known from the reported analyses (Table 1) andfrom nurnerous spectrographic analysesmade during the present study,
that the minerals of the gummite zone of alteration are essentially
hydrated oxides of uranium and lead. Barium, calcium, thorium, andalkalies often are also present in significant amounts in addition to lead.
For practical purposes of identification, the minerals that fall into thisgeneral region of composition may be divided into two groups. The firstg(oup, comprising curite, clarkeite, becquerelite, billietite, and MineralA, are relatively easy to identify in the present connection becausetheir
r-ray patterns are distinctive and their optical and other properties arealso diagnostic. The second group, comprising fourmarierite, vandendriesscheite,schoepite, Mineral C, masuyite, and richetite' are difficult
to identify. The r-ray powder patterns of all of these substancesare very
similar, and in the caseof faint or diffuse patterns or of mutual admixture
a positive discrimination becomesdifficult or impossible by this method.
In this case,the optical proprties are of aid: schoepite without lead hasmuch lower indicesof refraction than the others, with 7:1.74; vandendriesscheiteand Mineral C have indices usually in the range 1.76-1.85;
fourmarierite has higher indices, between 1.84and 1.96for the most part;the problematic mineral richetite is said to have I and I from 2.00 to
2.07; masuyite has a 1.785,P I.906, t 1.917accordingto one description
and B 2.I1, I 2.15 according to another. Complete optical descriptions

554

CLIFFORD FRONDEL

are given in Table 3. In the present study, the standard *-ray patterns
employed were obtained from type analyzed specimensof these minerals(with the exception of richetite, for which data and specimensare lacking). The *-ray pattern of masuyite is virtually identical with that ofvandendriesscheite.The identification of these minerals in gummite wasregarded as certain only if both the optical properties and the r-ray
pattern answered the standard description. If, as was often the case,theoptical properties were divergent or the optical properties answered thedescription and the r-ray pattern was diffuse and ambiguous, the identification was regarded as tentative. This procedure is not wholly satisfactory, as there are many uncertainties about the mutual relations of
the minerals here classedtogether. Thus it is an open question whether
the composition of these minerals is fixed, or whether there is a partial orcomplete variation in composition in point of lead content, with attendant variation in the r-ray pattern or optics, between some or all of them.
Further, it is not known how the presenceof barium or calcium in solid
solution for lead affects the x-ray and optical constants. This is an important factor in the case of fourmarierite and vandendriesscheite atleast. The barium and calcium analogues of fourmarierite have beensynthesized.rThey are isostructural with fourmarierite, and complete
series probably extend between all three members. The barium uranyloxide billietite was not identified in gummite, but it was observed as
sharp crystals coating cracks in a fourmarierite pseudomorph after uraninite from Katanga. In the latter specimenthe complete sequenceof deposition was uraninite (core), fourmarierite, billietite, uranophane, torbernite.
Fourmarierite was identified in gummite from the following localities: Wcilsendorf, Bavaria; Tvedestrand, Norway; as an alteration ofpitchblende from an unstated locality in Bohemia, probably Joachimsthal; Bisundi, Rajputana, India; the Spruce Pine district, MitchellCounty, North Carolina; Newry, Maine; the Katanga district, Belgian
Congol Mica Lakes area, Ifahns Peak, Colorado. It also was found as
thin colloform crusts on altering uraninite from Great Bear Lake, Canada. Some of the material from these localities had indices of refractionslightly higher than those reported in the literature, with gamma 1.951.97. Fourmarierite was doubtfully identified as a minor constituent ofgummite from a number of localities, including Morogoro, Tanganyika;
Rajputana, India; the Palermo and Ruggles pegmatites in New Hampshire; Pamplonita, Colombia (with z a little over 2); the Ingersoll mine,
Pennington County, South Dakota; Bathurst, Lanark County, Ontario;r By Miss Eleanor R. Berman, Department of Mineralogy, Harvard
University, 1954.

MINERALCOMPOSITION OF GUMMITE

5J.')

Wilberforce, Cardiff Township, Ontario. The mineral occurs as dense,
microcrystalline aggregates, and the color is orange red. The color islighter than that of curite. There is no question but that the indices ofrefraction of the mineral vary by at least 0.04 due to variation in composition, presumably the substitution of Ba and Ca for Pb.
Sarkar and Sen (1946) made an *-ray powder study of an orangeyellow gummite from Rajputana, India, which encased a residual of
uraninite and was in turn surrounded by lemon-yellow uranophane. They
concluded that the mineral was gummite (which they accept as a species
name) from the near agreement of their d-spacingswith the data given
by Ross, Henderson,andPosnjak (1931) foran unanalyzedspecimenof
gummite (in the broad sense) from Mitchell County, North Carolina.
This pattern is of the fourmarierite type but cannot be more closely
identified. The optical properties given by Ross, Henderson, and Posnjak(a L742, P I.762, y 1.776,2V 60", r(u) difier from thoseof fourmarieriteand vandendriesscheite but may represent Mineral C. Clarkeite andfourmarierite(?) were recognizedin gummite specimensfrom Rajputana
during the present study. Two partial analysesof impure gummite from
Rajputana cited by Krishnan (1948) show 8.26 and 19.10per cent PbO.
Crookshank (1948) describessome of the minerals from the Rajputana
pegmatites.
K asolite, Pb (UOr) (SiOr)(OH) r( ?)Kasolite occurs in the silicate zone of alteration as earthy to firm
microcrystalline aggregatesof minute shredsand fibers. Distinct euhedral
crystals such as characterize the Katanga material were not observed.
The mineral has a brownish-yellow to pale-brown color, and closely resembles the isostructural speciesMineral B (which see). It often occurs
more or less admixed with shreds and fibers of uranophane. Kasolite was
identified as the principal or sole constituent of the outer silicate zone inuraninite pseudomorphs from Kakanas and Gordonia, Africa; the Ruggles pegmatite, Grafton Center, New Hampshire; and Bisundi, Rajputana, India. It also was observed as a very minor constituent of thesilicate zone in material from the Morogoro district, Tanganyika, and a
few other localities. At the Ruggles pegmatite, kasolite occurs both as athin outer crust about the orange gummite pseudomorphsfor which thelocality is noted and as complete pseudomorphs of a rather porous consistency.
P hosp hur anyli t e, C a(U Oz)4( P Ot, (OH) r' 7HzO( ?)Phosphuranylite was observed admixed in small amounts with uranophane in the surfaceparts of altered uraninite crystals from Spruce Pine,

556

CLIFFORD FRONDEL

Mitchell County, North Carolina, and the Ruggles pegmatite, GraftonCenter, New Hampshire. Cubical molds of uraninite crystals, some empty
and others more or less completely filled with golden-yellow, earthy
phosphuranylite were noted in specimens from the Flat Rock mine,
Mitchell County, North Carolina; thesepseudomorphs,however,appear
to be due to the infilling of empty cavities (casts) and not to the alterationof uraninite in place. Phosphuranylite occurs much more commonly as
films and coatings on fracture surfacesin the immediate neighborhood of
uraninite pseudomorphsin pegmatites (Frondel, 1950). An occurrenceof phosphuranylite(?) with gummite and uraninite in eastern Kuangsi
province, China, is describedby Nan and Wu (1943).
Rutherford.ine,(UOr) ( COa)
Earthy, yellow pseudomorphs of rutherfordine after uraninite crystals
were described by Marckwald (19C6)from a pegmatite in the Morogoro
district, Tanganyika, Africa. Specim'ensexamined from this locality
showed a central core of uraninite, a surrounding zone of orange-red
gummite, and a pulverulent outer zone of. rutherfordine usually muchadmixed with uranophane and kasolite. The mineral occurs similarlyin pegmatite at Newry, Maine, and Beryl Mountain, New Hampshire.
A description of the mineral from its known localities is given by Frondel
and Meyrowitz (1956). Rutherfordine efiervescesstrongly in dilute acids,
although the reaction starts slowly, and this provides a useful aid in its
recognition. The mineral often is much too fine grained for satisfactory
optical study, and an r-ray powder pattern may be required. The uranyl
carbonates sharpite and studtite and tfre carbonates of uranium containing additional cations, such as liebigite, were not encounteredin thisstudy. In its known occurrencesrutherfordine appears to be producedby the action of carbonated surface waters on the hydrated oxides of thegummite zone.
Schoepite,2UOB'sHrO(?)
Only one example of schoepite was observed in the gummite zone ofalteration. It occurs as golden-yellow to yellow, earthy pseudomorphs
after uraninite in the Beryl Mountain pegmatite, near Acworth, New
Hampshire. Fine-grained Mineral B, uranophane, and rutherfordine
were associated. At Katanga, the principal locality for the mineral,
schoepite is a drusy or granular massive deposit from solutions and is
not a pseudomorphic alteration product. Hacquaert (1921), however,has noted its presence with becquerelite in a uraninite pseudomorph
from this locality. fts rarity in gummite is due to the general presenceof
lead, which leads to the formation of hydrated oxides such as vanden-MINERALCOMPOSITION OF GUMMITE

driesscheite and fourmarierite. Schoepite also was observed as a yellow
crust on massive uraninite from Hottah Lake, Canada, and from the
Delta mine, San Rafael Swell,Utah.
M g(UOz)z(SiOtr(OH)r' 5HrO
Shlod.ouskite,
Sklodowskite was not identified in the present study among the uranium silicates comprising the outer zone of alteration. It has been observed, however, by Hacquaeft (1927) with curite and cerussite comprising pseudomorphsafter uraninite from Kasolo, Katanga'(UOt6(SiO4)r(OH),' 5HrO
S od.d,yite,
Soddyite was identified only once in the present study, although its
presencein very small amounts admixed with uranophane was suspected
in material from a number of localities. It occurs abundantly at the
Ruggles pegmatite, Grafton Center, New Hampshire, as complete pseudomorphs after uraninite. These are yellow to straw-yellow in color, witha dense to almost pulverulent consistency, and are composed of minuteshredsand fibers of soddyite admixed with small amounts of uranophane.
In the hand specimen they resembled very closely the earthy types ofuranophane and Mineral B pseudomorphsfrom this and other localities.
Soddyite also has been found in the Norrabees pegmatite in Namaqualand, South Africa (Gevers, Patridge, and Joubert, 1937), where it presumably is an alteration product of uraninite. Soddyite may be present
in a gummite pseudomorph from Alto do Tibiri, Paraiba, Brazll, analyzedby Florencio(1951) (column 14, Table 1). Microcrystallinesoddyite is rather similar optically to beta-uranophane and phosphuranylite,
although it lacks the distinct golden pleochroism of the latter, and is best
identified by r-ray methods.
(I r onophane,Ca(UOr)z(SiOa)r(OH)r' 5HrO
The occurrenceof a calcium uranyl silicate in the outermost, greenish
zone of alteration of uraninite pseudomorphs, bordering on and veining
the orange-red gummite zorre, was established chemically by Genth(1879) and Von Foullon (1883) in material from pegmatitesin MitchellCounty, North Carolina. A probably identical mineral occurring as analteration of uraninite from Arendal, Norway, was analyzed by Nordenski<ild (1884). The existenceof uranophane in the siliceous outer zone insuch pseudomorphsalso was noted by Hidden (1881)' Tipper (1919),
Hacquaert (1927), Ross, Hendersonand Posnjak (1931)' Ellsworth andOsborne (1934), Bu'ttgenbach (1922), Schoep (1921), Sarkar and Sen(1946), and others. The first specimensent to Belgium after the discoveryof uranium in Katanga in 1913was describedby Buttgenbach (1926) as

JJ6

CLIFFORD FRONDEL

pitchblende altered to gummite and uranophane. This mineral has beencalled uranophane (or uranotil) in the older literature, but it was shownby Nov6dek (1935) and Steinocherand Nov6iek (1939) that the compound is dimorphous, orthorhombic (uranophane) and monoclinic (betauranophane). The distinction between these polymorphs rests chiefly on
optical and *ray criteria.
There is also the question of the identity of uranophane and uranotil.
Both names are found in some modern literature, as distinct species,
based on the belief that the acicular calcium uranyl silicate from Wcilsendorf, Bavaria, described by Boiickf (1370) under the name uranotil
difiers in composition from the very similar mineral described earlier
from Kupferberg, Silesia, by Websky (1853) as uranophane. Websky,sanalysis unfortunately was made on very impure material. An *-ray andoptical study made here of uranophane from Kupferberg and of uranotilfrom Wcilsendorf has shown conclusively that these two minerals are
identical. The name uranophane (and beta-uranophane) should be employed for the species,as was already concluded by Dana (1892).
The uranophane of the silicate zone of alteration generally appears
as a hard, dense mass, without structure visible to the unaided eye, andhas a waxy to subvitreous luster. The color of the mineral commonly isa pale greenish yellow, but varies to yellowish green, dull green, yellow,
orange yellow, and straw yellow. Occasionally it forms relatively soft toporous masseswith a dull to earthy luster and a straw-yellow to brownish-yellow color. Under the microscope, the mineral is microcrystalline
and composedof shreds or fibers in a confused or matted array. There isalmost always at least a small degree of admixture with other minerals.
The indices of refraction may be difficult to obtain accurately, becauseof
small particle size. Beta-uranophane, which otherwise resembles thepresent speciesvery closely, has higher indices and the extinction is inclined (Table 3). The ic-ray patterns of the two minerals are quite different (Table 4). Uranophane (and beta-uranophane) ordinarily are separated from the central core of uraninite pseudomorphsby an intermediatezone of gummite, from which the silicates have been derived. In a few
instances, however, uranophane was observed forming directly fromuraninite.
Uranophane was identified as the chief constituent of the silicate zone
in specimensfrom a large number of localities. These included numerous
places in the pegmatite districts of North Carolina, New Hampshire,
Maine, Connecticut, Colorado, and the Black Hills, South Dakota.
Among the foreign localities may be mentioned Calamuchita, C5rdoba,
Argentina; Rajputana, India; Karelia, Russia; Katanga, Belgian Congo;
Morogoro, Tanganyika. The mineral also was identified as fibrous crusts

MINERAL

559

COMPOSITION OF GUMMITE

and aggregatesassociated with altering uraninite, but not pseudomorphous after it, from Lake Athabaska, Saskatchewan,and Theano Point,
Lake Superior, Canadal Joachimsthal,Bohemia; Katanga district, Belgian Congo; Wiilsendorf, Bavaria; the Grants area, New Mexico; theMarysvale and Henry Mountains districts, Utah.
A specimenfrom Mitchell County, North Carolina, showed a uraninite
cube that had been wholly altered to a soft, porous, straw-yellow aggregate of uranophane. A chemical analysis of this material by F. A. Gonyer,cited below, is of interest in showing the presence of a considerable
amount of thorium and vttrium in substitution for calcium. A semiCaO
5.77

ThOz and
Y:O:
2.60

UOa

SiOz

HzO

Total

66.40

13.40

tl .7l99.88

quantitative spectrographic analysis by H. C. Harrison showed that Y
composedabout 10 per cent of the mixed (Th, Y) oxides. Optically, thismaterial had a-1.642 (nearly colorless), ?-1.668 (pale yellow) in Na
light, with Z paruIlel to the elongation.
V and,end,riesscheite,PbO' TUO3' I2}IIO (?)
The problems attending the identification of vandendriesscheite
have been discussed earlier under fourmarierite, which see. Vandendriesscheitewas identified in gummite pseudomorphsfrom the following
localities: numerous places in the Spruce Pine district, Mitchell County,
North Carolina, including the Wiseman, McKinney, Deak and various
unstated mines in this district; Newry, Maine; the Palermo and Ruggles
pegmatites in New Hampshire; numerous specimensfrom the Katanga
district, Belgian Congo;Joachimsthal,Bohemia. The mineral also occurs
as crusts and minute crystals (the "Mineral X" ol Palache and Berman,
1933) on altering uraninite at Great Bear Lake, Canada. It was observed as their colloform films on uraninite from Hottah Lake, N.W.T.,
Canada. Vandendriesscheite was doubtfully identified from a numberof other localities, and the mineral appears to be more common thanfourmarierite. It often occurs admixed with other oxidic minerals of both
higher and lower indices, and uranophane is commonly present in small
amounts. Vandendriesscheiteoccurs as densemicrocrystalline aggregates.
The color varies from yellow-orange, brownish orange' and orange toorange-red. The reddish shadesare less typical than with fourmarierite.
Usually only the mean index of refraction can be measured due to small
particle size; this varies from about I.77 to 1.82. Some material doubtfully identified as vandendriesscheitehad a as low as about l.7I-1.74'
There seemsto be little doubt that the indices of refraction of this min-

560

CLIFFORD FRONDEL

eral vary over at least 0.04 due to compositional variation, presumably a
substitution of Ba or Ca for Pb.
U nid,entif.ed.M iner al, AThis mineral was recognized in the gumrnite zone of specimensfrom
six localities: pegmatites at North Wilton, Palermo, Ruggles, Alstead,and Beryl Mountain, all in New Hampshire, and a pegmatite at Grassy
Creek, Mitchell County, North Carolina. The latter specimenwas one ofthose described and analyzed by Von Foullon (1883) in his study ofgummite. Mineral ,4 is particularly abundant at the Ruggles locality,
where it is one of the chief constituents of the orange gummite pseudomorphs after dendritic aggregates of uraninite crystals for which thelocality is noted (see Shaub (1938)). The mineral was recognizedas a
distinct and presumably new species on the basis of its r-ray powder
pattern (Table 4). ft occurs as microcrystalline aggregatesof a brightorange to orange-yellow or golden-yellow color. The reddish shades ofcolor seenin many fourmarierite and some vandendriesscheitespecimens
are lacking. The luster varies from dull and earthy to weakly vitreous in
hard, translucent aggregates.Under the microscope the mineral is yellow in color, not perceptibly pleochroic, and has low to moderate birefrfngence. Only the mean index of refraction could be obtained. Thisvaries between 1.78 and 1.88 in most specimens,but one specimenfrom
the Ruggles pegmatite had n-|.96. Semiquantitative spectrographic
analyses show that the mineral is an oxide of uranium or a uranate containing Pb, K, Na, Ca, and Ba in significant amounts. The Ruggles material with n-1.96 contained Pb between 5 and 10 per cent, K and Ca
0.5-1 per cent, Na and Ba 0.1-0.5 per cent. Material from Palermo withn-l.84 containedboth Pb and K in the range 1 to 5 per cent, and Ca,Ba
and Na in therange 0.1 to 0.5 per cent. Possibly several different isostructural minerals varying in the mutual substitution of Pb, K, Ca,
etc., with accompanying variation in the indices of refraction, are represented. The r-ray patterns of all specimensare virtually identical. There
was a complete change in the r-ray pattern of the Ruggles material after
heating to 500" C. Study of this mineral is continuing.
U nid.entif,ed. M ineral B
Mineral B, apparently the calcium analogue of kasolite, is a relatively
common constituent of the silicate zone of alteration. It was first recognized as a probable new speciesduring the present study, and a detailed
description is in the course of preparation. Mineral B occurs as dense toearthy microcrystalline aggregates composed of minute shreds andfibers. Its color is straw yellow to pale yellowish brown, and lighter than

MINERALCOMPOSITION OF GUMMITE

561

typical kasolite. The r-ray powder pattern is virtually identical with thatof kasolite, but the indices of refraction are cobsiderably less (Table 3).
The presence of calcium as a major constituent was established bychemical tests. The mineral often is so fine grained that only the mean
index of refraction can be obtained; this usually rangesbetween 1.81and
1.84.Admixture with uranophaneis common. Mineral B occurs both ascompletepseudomorphsand as zonessurrounding orange-redgummite;it also has been observed as earthy crusts along fracture surfacesin thematrix. The mineral was recognized from the following localities: theBob Ingersoll pegmatite, Pennington County, South Dakota; the Ruggles pegmatite near Grafton Center, and the Beryl Mountain pegmatitenear Acworth, both in New Hampshire; the Mica Lake area, Hahn's
Peak, Colorado; and Bi5undi, Rajputana, India. It was doubtfully identified in material from Karelia. Russia, and several other localities.
U nid,entif,ed,M iner al C
This apparently new specieswas recognized on the basis of its cc-tay
powder pattern (Table 4). The pattern closelyresemblesbut is distinct
from the patterns of fourmarierite and schoepite. The pattern seemsto
be defi.nite and characteristic as it was given by natural material fromfive different localities and also by a sample of synthetic hydrated lead
diuranate. Mineral C occurs in the gummite zone of alteration as dense,
microcrystalline aggregates with an orange-brown, reddish-brown or
chocolate-brown color. The powder is mustard yellow. The color differsfrom the orange-red color of fourmarierite and some vandendriesscheite,
and the yellow to orange color of Mineral -4' Clarkeite, however, has avery similar color. The mineral was observed from the following localities: Mitchell County, North Carolina, at the Wiseman mine (analysis 4,
Table 1), the McKinney mine, and at an unstated locality (analysis12,
Table 1) I Easton, Pennsylvania,where it is an alteration of uraninite or
uranoan thorianite; Newry, Maine. The material from the Wiseman
mine is that describedby Ross, Henderson and Posnjak (1931). The
optics given by these authors for "gummite" do not refer to the present mineral; the material of their analysis sample, here examined, has
indicesbetween 1.77 and 1.82.A similar range is shown by the material
from the other localities stated, with the exception of the material ofanalysis 12, Table 1, from Mitchell County, which has higher indices,
1.85-1.89.The indicesare considerablylower than those of fourmarieriteand clarkeite, but comparable to those of vandendriesscheite.Schoepite
has much lower indices of refraction. The fine-grained nature of thematerial makes optical study difficult. The two available analysesof thismineral, cited in Table 1, were made on slightly inhomogeneousmaterial.

562

CLIFFORD FRONDEL

A semiquantitative spectrographic analysis of the Easton material
showedU as the major constituent with Th, Pb, Ca, and Ba present inamounts between 1 and 10 per cent. Mineral C apparently is related
structurally to fourmarierite. A further description of this mineral withadditional analysesis planned.
AcxNowrorcMENTS
The present study was done by the U. S. GeologicalSurvey on behalfof the Division of Raw Materials of the U. S. Atomic Energy Commission.
The writer wishes to expresshis appreciation to Mrs. Judith W. Frondel
for supplying new *-ray and optical data on vandendriesscheite andmasuyite, and to Miss Mary Mrose, U. S. Geological Survey, for aidingin the preparation of r-ray powder photographs. Mr. H. C. Harrison,
Rhode Island State College,kindly made a number of qualitative spectrographic analyses. Additional semiquantitative spectrographic analyses
were obtained through Miss K. E. Valentine and Mr. Charles Annell,
U. S. GeologicalSurvey. A number of specimenswere borrowedfor study
from the U. S. National Museum through the courtesy of Dr. George
Switzer. Thanks also are expressedto various members of the Boston
Mineral Club, particularly to Mr. Rudolph Bartsch, for their interestin supplying for study specimens of uranium minerals from pegmatite
Iocalities in New England. Mr. H. A. Ashley of North Rumney, New
Hampshire, generously gave a collection of uranium minerals from thePalermo and Beryl Mountain pegmatites and facilitated collecting at
those localities. Gummite specimensalso were obtained for study fromthe Royal Ontario Museum through the courtesyof Dr. V. Ben Meen.

MINERAL

563

COMPOSITION OF GUMMITE

Teur,n 3. Oprrcer, PnoprLrrrs ol Mrr.rpner,sPnrspxr rN GuMMrrE
Name

Symmetry

Indices and pleochroismaPa

Remarks

Becquerelite

Orthorhombic

r.72-1.75 1 81-1.82 1.82-1.83
pale
deep
deep
yellowyellowyellow

X perp. cleavage.

Beta-uranophane

Monoclinic

1 . 6 6 - 1 . 6 7 1. 6 8 - 1 . 6 9 1 . 6 9 - 1 . 7 1 ( - ) , 4 0 o - 7 0 o ,colorlesslemonlemonr>tyellowyellow

X:b,
ZAelons.
:18"-57o. Fibers.

Clarkeite

2.OO
2.10
2.rl
Color brown-yellow to reddish
brown

( -),
r<!

vary;
Indicessome with mean
index 1.94-1 97

mod.

CuriteOrthorhombic

2.O5-2.06 2.07-2lt
paleyellow light redorange

Fourmari eri te

Orthorhombic

1.85-1.86 1 90-t.92 t.90-1.94
paleyellow yellow tocolorlessto orange orauge(-), mod. tolarge r)o

X perp. cleav , Y: elong.

1 . 8 8 - 1. 9 0 1 . 9 0 - 1. 9 1 1 . 9 4 - 1. 9 6
Nearly colorlessto pale yellow(+),42'

X:eloug. Faintyellow pleochroism. Fibers.

(-), s0',

X perp, cleavAlso with indices2.1r-2.15 (?).

Kasolite

Masuyite

Orthorhombic

1.785
pale
yellow

1.906
deep
golden2 . 1 1 - 2 . 1 5 (-),large
dark redorange

1.917
deep
goldent>aMeta-autunite

Tetragonal

Mineral A

Not known

Mean inds 1 . 78-1.88,
variable

Mineral B

Monoclinic

Mineral C

Not knom

Phosphuranylite

Orthorhombic

1 . 6 6 - 16 7 1 . 7 0 - 1 . 7 2 7 . 7 0 - 1 . 7 2
pale
goldengoldenr >flyellowyellowyellow

Rutherfordine

Orthorhombic

1.721
pale
yellow

Schoepite

Orthorhombic

1 . 6 9 - 1 . 7 0 1 . 7 1 - 1 . 7 2 1 . 7 3 - 1 . 7 4 ( -), large
colorlesslemonlemont>ayellowyellow

Sklodowskite

Orthorhombic

1.613

Orthorhombic

1.65
colorless

1.68
pale
yellow

Uranophane

Orthorhombic

1.64
colorless

1. 6 6
goldenyellow

Vandendriesscheite

Orthorhombic

1.58-1.60 1.59-1.61 1.59-1.61 (-),0o to
paleyellowyellow
small, z)ryellowrlt

Z:elotg.

X perp. plates
and cleavage.Indicesand 2Vvary
with HrO

(*)

mod.

Yellow. Not Dleochroic (?). Alsowith a: 1 .96.

N1.84
1.825
1.867
Nearly colorless to pale yellow

(*)

mod.

Meanindex 1.811.83 when finegrained.. Faintpleocnrorsm,

Mean index 1.77-1.82, variable, in part higher?

(*)

mod

Orange-brown.
Not pleochroic ?

1.729
goldenyellow

1 . 75 7
greenish
Vellow(*),

Z perp. plates.
Indices increase
with Pb content.
large

X perp.
age.

cleav-

( -),

large

Y:elong

1.71
palegreenyellow

( -),
t>r

large

Often cloudy.

1.67
goldenyellow

(-),
r>0

sro]l

Z:elong.
lel.

1 . 7 6 - 1 . 7 9 1 . 8 1 - 1 . 8 4 1 . 8 2 - 1 . 8 5 ( -),goldengoldencolorlessr>tyellowyellow

med.

1 635
1.657
color pale yellow

Parul-

TesLr 4. X-Rav Pownnn Dete lon MrNrnnr-s rN Guuurtr
Copper radiation, nickel filter, in Angstroms
Note: In most instancesonly the inner linesof the patternsarecited, sufficientto ensure
discrimination.
Becquerelite

1
10
2
1
1
6
1
8
8
2
2
9
I
2

8.51
7.50
6.63
6.24
5.63
4.7r
4.31
3.75
3.56
3.48
3.39
3.22
3.13
2.97

Beta-uranophane

10
4
4
4
4
4
3
9

7.83
6.66
6.10
5.07
4.85
4.55
4.ll
3.90

r
6

3.75
3.51

1
2
5
4
3
2
4
3
5

3.47
3.35
3.19
3.04
2.99
2.91
2.83
2.78
2.59

Fourmarierite

Kasolite

2
4
9
10
4
6
5
2
2
6
8
2

6
2
4
2
8b

6.61
6.19
5.31
4.76
4.19

/

J.JJ

7.86
6.83
3.45
3.09
2.73
2.4
2.26
2.15
2.09
1.996
1.907
1.817

b:broad line.

1
10
5
9
3
3

3.38
3.26
3.07
2.93
2.73
2.64

CuriteClarkeite

1 10.98
8.33
1
2
6.70
I
5.77
4.09
4
9
3.34
10 3.17
2.92
3
2.69
5
4
2.61
2.45
3
2.06
2
7
r.968
1.863
6

Phosphuranylite

1 10.16
1 0 7. 8 3
r/2 7.2O
1
6.33
8
5.83

r/2 s.s7
|
2
3
9
1
r
2
6
4
2
6

4.96
4.72
4.33
3.97
3.83
3.4
3.36
3.r2
3.O7
2.94
2.86

10
1
4
1
9
4
4
8
4
2
|
4

6.28
4.80
4.55
4.r7
3.97
3.53
3.36
3.14
3.07
2.93
2.8r
2.70

Rutherfordine

J

4.60
4.27
3.87
3.20
2.62
2.48
2.41
2,28
2.14
2.04
r.94
1.91

2
2

r.87
L.7s

10
8
8
9
z
J

n

6
8
I

MINERAL

Tesrr 4. X-REv Powonn Dlu
Schoepite

10
1
2
2
8
9
1
2
7
3
2
|
1
4
6
I

7.49
6.74
6.09
4.08
3.64
3.26
3.01
2.83
2.60
2.48
2.35
2.27
2.21
2.tO
2.05
1.981

Vandendriesscheite

2
10
3
1
2
1
2
8
|
9
I
3
5
2
7
2
7
3
b:broad

8.27
7. 3 1
6.49
4.85
4.39
4.14
3.93
3.58
3.37
3.19
3.00
2.73
2.53
2.40
2.32
2.05
r.989
1.908
line.

lon Mrrnners rN GuMMrrE-Conti.nued,
Soddyite

Sklodowskite

10
2
5
4
1
4
8
5
6
7
6
5
2
2
1
|

565

COMPOSITION OF GAMMITE

8.42
6.37
5.91
4.82
4.51
4.33
4.19
4.00
3.52
3.27
3.00
2.87
2.80
2.74
2.70
2.66

8
3
9
2
10
2
3
2
7
6
|
2
2
1
4

Uranophane

6.14
4.71
4.48
3.73
3.32
3.22
2.95
2.78
2.69
2.47
2.39
2.32
2.26
2.18
2.09

10
4
4

7.88
6.61
5.42

J

+./O

2
9
4

4.29
3.94
3.ffi

{t

J.Jl

1

3.41

I

J.JJ

5
I
8
I

3.20
3.09
2.99
2.91

Mineral A

Mineral C

7
10
7b
5
3b
7
2
3b
I
3
I
|

5
1
|
10
10
|
3
2
5
6
6
4
2
1
2
1
2
2

6.37
3.49
3.18
3.02
2.61
2.09
2.O0
t.92
1.81
1.75
1.57
1.52

6.95
5.85
4.12
3.46
3.09
2.77
2.44
2.29
1.991
1.916
1.730
r.673
1.548
1.509
1.383
1.355
1.305
1.283

CLIFFORD FRONDEL

566

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568

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