THE CORREGO FRIO PEGMATITE, MINAS GERAIS:SCORZALITEAND SOUZAI.ITE,TWO NEW PHOSPHATEMINERALS1
Wrr-r-rRuT. Pncone aNo Josnrn J. Fannv,
U. S. GeologicalSuraey, Washington, D. C.
Tlst-n or CoNrnNts

83
84
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91
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93

Introduction and acknowledgments. .
Location
History.
R e g i o n a lg e o l o g y . . . . . . .
T h e C o r r e g oF r i o P e g m a t i t e . . . . . .
Descriptive mineralogy.
Minerals in the pegmatite . .. .
Scorzalite

Souzalite..
Brazilianite.
Otherminerals.. .
Genesis.
References
Asstnecr

This paper describes the structure and mineralogy of a pegmatite that has yielded three
new phosphate minerals in recent years. The pegmatite is well zoned into three structuralunits of characteristic texture and mineral association. The minerals present include albite,
muscovite, quartz, scorzalite (new mineral), souzalite (new mineral), brazilianite, apatite,
zircon, tapiolite, and two unidentified phosphate minerals. Detailed descriptions, withchemical analyses, are given for scorzalite and souzatte, both of which are hydrous ironmagnesium aluminum phosphates. Scorzalite is isomorphous with lazulite; the structural
relationships of souzalite are not known.
INrnopucrtoN

AND AcrNowr-BUcMENTS

This paper contains a detailed description of the structure and mineralogy of the Corrego Frio pegmatite, Minas Gerais, BtaziT, which has
yielded three new phosphate minerals since its discovery in t942. Twoof these new minerals, scorzalite and souzalite, are described in thispaper. Additional information on brazilianite, described in 1945, is alsopresented.
The authors are indebted to a number of colleaguesin the Section ofGeochemistry and Petrology, U. S. Geological Survey, for courteous assistancein mineral study. K. J. Murata made spectrographic analysesof
scorzalite and souzalite that served as a guide for the chemical analyses
by Fahey. J. M. Axelrod took r-ray powder diffraction photographs of
I Published by permission of the Director, U. S. Geological Survey. Paper read before
the Mineralogical Society of America, Ottawa, Canada, December 30, 1947'

83

84

W, T. PECORA AND J. J. FAHEY

the new phosphate minerals and prepared the mount reproduced in figure
3. E. S. Larsen 3d was helpful in the precise determination of the opticalconstants of scorzalite and souzalite. Theodore Botinelly made microchemical tests for phosphorus and other elements in two unidentified
minerals in the collection. Marie L. Lindberg assisted in purifying rwo
samplesfor analysis. E. S. Larsen 3d, Michael Fleischer, and Earl Ingerson, all of the GeologicalSurvey, critically reviewed this paper and madeseveral suggestionsfor its improvement.
LocerroN
The Corrego Frio pegmatite is in eastern Minas Gerais, Brazil (seeFig. 1) near the village of Divino and approximately 40 km. north of
STAIE OF
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s----r,-----i
i P.smorrt. tocot-rtt

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t
t

a,
corstrxtrlo

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Frc. 1. Index niapof a part of southeastern Brazil showing the location of theCorrego Frio pegmatite in the municipio of Conselheiro Pena,eastern Minas Gerais, Brazil.

FRIO PEGMATITE, MINAS GERAISCORREGO85

the vics6o Tom6-a small town in the Rio Doce valley connected bytoria-Minas Railroad with the cities of victoria and Belo Horizonte.

in detail.
Hrsronv

new sodium aluminum phosphate, by Pough and Henderson (1945)'
In late lg44,E. R. Swoboda,an American mineral dealer, aware of therarity of the crystals, obtained a lease on the locality and supervised
additional excavation of the pegmatite. In 1945 and 1946 Mr' Swoboda
ofiered.brazilianite crystals for sale to mineral museums' mineral dealers,and mineral collectorsin the United States.
The pegmatite locality was visited by the senior author (WTP) inof the pegmatites of;une 1O4i in connection with geological studies
on this visit
collected
specimens
of
To
suite
the
Gerais.
eastern Minasforspecimens
choiceofhisnumberagenerously
donatedMr. Swoboda
mineralogical study.
Rncrorar

Grorocv

Eastern Minas Gerais is for the most part underlain by dark-colored
schist and gneiss,light-colored granitoid gneiss, and sericitic quartzite.
All of these rocks are assignedby Brazilian geologiststo the pre-Cam-letin, in preparation).

86

W. T. PECORA AND J. J. FAEEYTsB Connnco Fnro Pncuerrrn
The pegmatite exposed at the head of Corrego Frio strikes approximately east-west,dips steeply to the north, and is a tabular mass essentially in alignment with the schistosity of the biotite-garnet schist containing it. The pegmatite (Fig. 2) is exposedfor about 1g meters on thesurface and about 10 meters vertically. rts thickness ranges from threemeters at the surface to one and one-half meters in the lower cross-cur
adit shown in Fig. 2. A second pegmatite, probably similar to the one
described in this paper, is partly exposed in the stream bed about 100
meters to the south
On the basis of texture and mineral composition, the pegmatite can be
subdivided into three units, named, from border to center (1) the massive border zone, (2) the crystal cavity zone, and (3) the quartz lens.
Each of these units, illustrated in Fig. 2, is describedbelow.
The massive border zone is exposed on both margins of the pegmatite where its contact with wall-rock schist is regular and well defined.
At the surface (seesketch B-B') the two border unit. ur" equal in thickness,and together they make up about two thirds of the thickness of thepegmatite. rn the lower adit the unit on the north side (hanging wall) is
thicker, but the two units make up the sameproportion of the pegmatite.
rn thickness the unit ranges from 30 cm. to one meter. The border zone
is composedprincipally of massivealbite and subordinately of quartz andmuscovite. The cleavagefaces of the albite are as much as 15 cm. wide.
Thin, elongate, blue-green masses (scorzalite and souzalite), up to 25cm. long, extend acrossthe zone normal to the contact.
The crystal cavity zone has an irregular, poorly defined contact withthe massive border zone.rt ranges in thickness from a few centimeters,

stained muscovite. cleavelandite and porous and massivealbite all occur
in this zone, and in general, a higher proportion of. quartz and muscovite
occur-herein the pegmatite.
The quartz_lenshas been almost entirely removed by mining. According to the miners, it was originally exposed on the surface for about 5
meters along the strike, where it had an estimated thickness of between
one-half and one meter, and gradually thinned to disappear at a depthof about 4 meters. The lower edgeof the lens was irregular and had a perceptible rake to the east. The unmined portion of the quartz lens, shownin Fig. 2, is bordered by a mixture of cleavelandite and muscovite.

87

CORREGOFRIO PEGMATITE, MINAS GERAIS

I eaniliiii
iiiiiri

lilir
(liit

titi

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il,iiliitit

EXPLANATION

ffi

Oudlt l€ns

[ilitl.tl

ffi

Cryslol covity tonc-lMossivebordat :onaiiiiilili
rilrriililir

ITTI|
Schist
I

o

I

I

t

a

lrEr€lt

sketchesof the CorregoFrio
Frc, 2. Longitudinal profile and two cross-section
pegmatiteshowingits zoning and structural relations.

W. T. PECORA AND J, J, FAHEY

Dnscnrprrvn MrNnnarocv
Minerals in Lhepegtnatite
Albite, muscovite, and quartz make up more than 99 per cent of thepegmatite. Six phosphate minerals are present including scorzalite andsouzalite-two new hydrous iron magnesium aluminum phosphates;
brazilianite, a hydrous sodium aluminum phosphate first described in
1945;blue-greenapatite; and two unidentified phosphate minerals. Tapiolite and zircon are rare accessoryminerals. Beryl and tourmaline, foundin the stream bed below the pegmatite, are not present in the mineralcollection studied, nor were they observed in the exposed parts of thepegmatite.
Scorzal,ite
Scorzalite (scor'-za-lite) is named after Dr. Evaristo Pena Scorza,
chief mineralogist of the Departmento Nacional da Produgao Mineral,
Rio de Janeiro, Brazil. It is dark blue, massive,and occurs principally inthe border zone and outer margin of the crystal cavity zone. The largest
mass of scorzalite observed is about 7 cm. across, and the massesare
rarely free froni admixed souzalite.
The physical properties of scorzalite are given in Table 1 and its chemical analysis in Table 2. The analysis gives the formula (Fe", Mg)
Alr(PO4)r(OH)2,with Fe:Mg:2:1.
This formula, which may also be
written (Fe, Mg) O.Al2Oa.PzOo.HzO, is analogousto that of lazulite.The
two minerals are similar in appearance and have, as shown in Fig. 3,
identical c-ray powder difiraction patterns. They form a complete isomorphous serieswhich is now under detailed investigation by the authors. ft is here proposedthat the seriesbe characterizedbythe two names
lazulite (Mg dominant) and scorzalite (Fe dominant). fntermediate
members are named by the use of adjective modifiers. Thus the scorzalite
from Corrego Frio might be termed magnesianscorzalite.
Scorzalite has higher indices of refraction and higher specific gravity
than lazulite, as shown in Table 1 by a comparison of lazulite (Mg:Fe:8:1) from Chittenden, Vt. (Palacheand Gonyer, 1930)with scorzalite
from CorregoFrio (Mg: Fe: 1 : 2).
Souzalite
Souzalite (sdze'-a-lite)is named after Dr. Antonio Jos6Alves de Souza,
former Director of the Departamento Nacional da Produgdo Mineral,
Rio de Janeiro, Brazil. The mineral is green and occurs in irregular,
fibrous massesso intimately associatedwith scorzalite that it is believed

89

CORREGO FRIO PEGMATITE, MINAS GERAIS
T.lsr.n 1. Pnvsrcer-Pnopsnrrrs or Sconzr-nr' elo Souz'lrnn rnou
Mnces Grners, Aro Lazul.rtr rnou CrrttnxnrN, Vt'
Souzalite
Color (hand spec.)
Habit

dark blue
masslve

Specific gravity
Hardness
Crystal system

3.268(pycnom.)
6
Monoclinic

dark green
coarse fibrous aggregate
3.087 (pycnom.))z1.633 (colorless)1.663 (blue)
1.673(blue)

Monoclinic (?)

1 .618 (green)
1 .642 (blue)
1 .652 (yellow)

1.604 (colorless)1.633 (blue)
1.642 (blue)
64'(calc.)

2V

(-)

Optical character
Dispersion of the
optic axes

dark blue
massive
2.96
5-6
Monoclinic

s+-6

lndices of Refraction

Na lx(10.002)| Y

Lazulite/<?,, percept.

Twinning
multipler)rr, extreme andsymmetrical

r<?, percept.

polysynthetic twins,
max. extinction
12o; comp. pl.
parallel to goodcleavage

Cleavageone good cleavage,
approx. at rightangle to faircleavage

Orientation

X-lcleavage plates;
Z: elongation(near c?)Good

to be a hydrothermal alteration product of scorzalite. The largest mass ofsouzalite observedis 10 cm. across.
The physical properties of souzalite are given in Table 1 and its chemical analysis and formula in Table 2. Souzalite, like scorzalite, is a hydrous magnesiumiron aluminum phophate but its formula is of a difierent
type: (Mg, Fe")3(Al, F""')o (POn)n(OH)u'2HzO. The r-ray powder pattern of souzalite (shown in Fig. 3 and in Table 3) does not resembleanyof about 25 phosphate minerals with which it has been compared.
Becausethe type souzalite from the Corrego Frio pegmatite occurs as

90

W, T. PECORA AND J. J. FAEEY
Tl.nte 2, Cnnurc.u, Ar.ur,vses aNo Morocur,er Rarros ol Sconzalrrn
ANDSouzAurE mou Mnvas Gnners, Bn.lzrr,$. J. Fahey, ana.l.yst)
Scorzalite

Souzalite

Per cent

Ratio

Per cent

AhOa
FeeOa
Tioz

30.87
.54
.10

.30281.00341 .s073 0.98

26.07
2.65
.07

FeO
MsO
MnO
ZnO

14.74
4.23

SnO
CaO

none
.02

PzOs
HrOHrO+

42.90
none
5.86

Total

.001lj.311m 1.01

.2ss7l.0166i .2732.000eJ

2.04

.4036

3.00

.2656

.2656

1.98

.6681

.6681

4.98

11.49
9.62
.31
none

.04
.02
.3022

.3022

A.97

37.70
none

.3252

99.54

FormulaRrOs.RO. PrO6.HrO
Mol. ratio MgO:FeO:1:2

.3252

l.O4

12.04
100.01

2RzOa.3RO.2&O5:5H2O
Mol. ratio MgO:FeO:3:2

Note: fn the blowpipeflame,both mineralsareinfusibleand disintesrate.Both minerals
are solublewith diftculty in HCl.

Frc' 3. X-ray powder difiraction photographsof scorzaliteand souzalitefrom the Corrego
Frio pegmatite,Minas Gerais,and oI lazulite from GravesMt., Georgia.

9I

CORREGOFRIO PEGMATITE, MINAS GERAIS

coarse,fibrous, twinned aggregates,the optical constants given in Table
1 are less reliable than those determined for scorzalite. The powderedmineral in immersion shows positive elongation, one very good cleavage
normal to the Bx, and a diagnostic dispersion of the optic axes.
Tnsrr

3. Mrasunno d SplcrNcs ol X-tlv Poworn P,q'rronr.r Prrotocnnpn
Souzarrrp FRoM Tr{E Conntco Fnro Pncuarrrn

Legend: VS:very
F:faint;(Filtered Cu radiation, I:1.5418 A)
MW:mediumstrong; S:strong; M:medium;
B:broad.

ol

weak; W:weak;(measurementsby E. A. Cisney)

Intensity

Intensity(3)s.3s( 2 )3 . 7 e
J..)/

3.25
2.852
(1) 2 .6e0

2.sosl2 "4721
2.$6)
2.324
2.246
2.027
1.920
1.894
1.868
1.794

S
S
F

w
w
VS
S
M
F
S
F

w
w
F

1 .665
1.629
t.574
1.530
1.511
r.44
1.418

r.376
1.348
1.320
1.228
|.2r8
1.183
t.169
1.015
.898

F
MW

w
MW

w
MW
F
F

w
MW
MW

w
F
F
MB
WB

.Brazil,ianite
The mineralogy of brazilianite from this locality has been described by
Pough and Henderson(1945),Tavora (1945),and Hurlbut and Weichel(1946). A second occurrence of brazilianite in the Palermo pegmatite'
North Groton, N. H., has been describedby Frondel and Lindberg (1948)'
George Switzer of the U. S. National Museum, Washington, D. C',
examined thirty-seven new crystals from the Pecora-Swobodacollection.
The crystals are all splendent, range in size from one-half to four centimeters across, and range in weight from less than one up to thirty-two
grams. The most completely developed crystals are doubly terminatedand have 20 to 30 faces. Switzer (personalcommunication) states: "Thecrystals have two habits, as describedby Pough and Henderson (1945).
The dominant habit is one with a narrow prism zone and considerable
elongation parallel to [100]. This habit is similar to that recentlv de-92

W, T. PECORA AND J, J. FAEEY

scribed for brazilianite from New Hampshire by Frondel and Lindberg(1948). In the less common of the two habits the prism zone is slightly
elongated.No new forms were noted in the Brazilian crystals."
According to available sources of information, about 30 kg. of gem
crystals and about 200 kg. of specimen"pound material" were recoveredin the period 1943-46.Many of the gem crystals were destroyed in preparation for or during lapidation. According to two miners, one large manyfaced crystal recovered in 1943 weighed about two kilograms and was
broken up in an attempt to acquire gem-clearpieces.The largest crystal
known to exist weighs approximately one kilogram and is on display in
the U. S. National Museum in Washington. About a dozen other crystals
are known whose weights range from 100 to 1,000 grams. Most of thecrystals are lessthan an inch acrossand weigh less than 10 grams.
The indices of refraction for brazilianite, as determined from a numberof specimens,are higher by 0.003 than those published by Pough andHenderson(1945),as shown below:

nX
nY
nZ

Earlier data
(published)' 1.598
1.605
1.617

New data(10.001, Na)
1.601
r.608
1,620

Other minerals

Apatite occurs as dark-green, hexagonal crystals up to 3 cm. across,commonly clear or gemmy in quality. As indicated by its indices of refraction (t,l:1.633 and e:1.630), the mineral is probably a nearly pure
fluorapatite.
Two unidentified phosphate minerals were noted in a few specimens.
One, a light-brown mineral, occurs as an irregular intergrowth with altered scorzalite and its optical constants are: biaxial (+), 2V:50o( e s t i m a t e d ) ;r ( u , s t r o n g ; n X : 1 . 6 0 7 , n Y : I . 6 1 9 , n Z : 1 . 6 3 2 ; c o l o r i n
immersion is yellow. The secondunidentified phosphate mineral occurs as
dark-brown prismatic crystals in tiny alteration cavities in the lightbrown phosphate mineral or in scorzalite. Its optical constants are:biaxial (+), 2V:2Qe (estimated); nX: (yellow-brown):I.705, nY:(dark-yellow):1.709, p2: (yellow): 1.735;orientation, X: elongation;orthorhombic (?).
Tiny bipyramidal crystals of colorlesszircon with the prism form subordinately developed are imbedded in a quartz-albite mixture and surrounded by the unidentified light-brown phosphate mineral.
Black, splendent, striated, tabular crystals of tapiolite are imbeddedin albite in a few specimens.The crystals range up to one centimeter inCORREGOFNO PEGMATITE, MINAS GERAIS

93

length. Its optical constants are: Uniaxial (*); birefringence, very high;c,r(brownish-red) and e (greenish) both higher than 2.0 (selenium tnelt);
Absorption E ) O, strong.
GBNBsrs
The well defined contact with schist and the texture of the borderfacies support the hypothesis of intrusion of a magmatic fluid which consolid.atedfrom border to center after emplacement. Similar relations exist
for hundreds of other pegmatites in the region in many difierent kindsof host rock. Accessoryphosphate minerals are common in many pegmatites near the Corrego Frio locality, but are rare in pegmatites of other
districts in Minas Gerais. Within the granitic petrogenetic province ofeastern Minas Gerais, with a locus in ConselheiroPena, is a subprovince
characterized by a relatively significant concentration of PzOo'With respect to other pegmatites in this subprovince, the Corrego Frio pegmatite
is especiallycharacterized by the presenceof the rare phosphate minerals brazilianite, scorzalite, and souzalite, and by the conspicuousabsenceof potash feldspar.
The sequenceof mineral formation in the pegmatite has not been established with certainty. The massive albite is characteristic of the earlystage of pegmatite consolidation, whereas cleavelandite has formed in
the late stage. Scorzalite, souzalite, and apatite are intermixed withmassive albite in the border zone and are included by crystals of brazilianite and qtJartz in the crystal cavity zone. Shell-Iike intergrowths ofapatite and massive albite in the outer margin of the crystal cavity zone
indicate that apatite began to form near the end of massive albite formation. The field relations support the hypothesis of continuous crystallizationfrom a magmatic to an autohydrothermal stage.
RBnBruNcns
FnoNorl, Cr-mrOno,l1o LrNonnnc, M. L. (1948),Secondoccurrenceof brazilianite: Am.
M ineral,.,33, 135-141.
Gooov, M. PnrBNmr.on (1945),Occurrenciasde brasilianitado CorregoFtio:. MinuaQd'oe
Metollwgi.a(Brasil), YlI, No. 48, 385-387.
Hunrnur, C. S., Jn., ero Wntcrer., E. J. (1946),Additional data on brazihanitezAm'
Mineral'.,31,507.
Prr.ecr, CuAnms, em GoNwn, F. A. (1930),Lazulite from Chittendgn,Yt': Arn'
M i,neraI., 15, 338-339.
Poucr, F. I{., eNo HnwonnsoN,E. P. (1945),Brazilianite, a new phosphatemineral Am'
M i.nera1,.,30, 572-582.
Tevonl, Er-vsrenro(1945),Constantescristallograficasda brasilianita: MinaoQdoe Metal'
lurgia (Brasil), YIII, No. 48,373-375.