American Mineralogist, Volume 70, pages I314-1317, 1985
Gysinite, Pb(Nd,La)(CO3)2(OH). HzO, a new lead, rare-earth carbonate
from Shinkolobwe, Shaba, Z{fie and its relationship to ancylite
Hlr,rr, S.lnp
Department of M ineralogy
GeneuaNatural History Museum
Route de Malagnou, 1208 Geneua,Switzerlanil
,q.Nr JSA,NBpnrntNo
Department of M ineralogy
Uniuersity of Geneua, 13, rue des Maratchers
l2l I Geneua4. Switzerland
Abstract
Gysinite,ideallyPb(Nd,La)(CO3)r(OH).HrO,
occursat Shinkolobwe,Shaba,Zaire,associated with schuilingite,malachite,cerussite,talc-chlorite, bornite, wulfenite, kasolite, native
gold and garnet.The crystals,light pink to reddish pink in color, up to I mm in length, are
euhedralwith a pseudo-octahedral
habit and with {111} and {ll0} as the most prominent
forms. The streak is white to light pink. The name is to honor ProfessorMarcel Gysin. The
crystal systemis orthorhombic, space group Pmcn, with a : 5.04,b : 8.50,c : 7.254 and
Z : 2. a:b:c ratio is 0.5929:1:0.8529.The calculateddensityis 4.82 glcn3.X-ray diffraction
data are similar to those of ancylite.The mineral is biaxial negativewith 2V*: 7O",24"r":
7 2 . 4 "u
, : 1 . 7 4 5 , B : 1 . 8 0 5 , 1 : 1 . 8 4 0 , d i s p e r s i orn< u . O p t i c a lo r i e n t a t i o nX: : c , y : a ,
Z:b.
Introduction
Gysinite was discovered on a single specimen from the
mineral collection at the Geneva Natural History Museum.
This sample, catalog #410185, was labeled schuilingite
from Shinkolobwe, Shaba, Zalre.
The name is in honor of the late Professor Marcel Gysin,
who taught mineralogy at the University of Geneva and
had worked for several years in the Shaba province of
Zaire. This new mineral and mineral name have been approved by the Commission on New Minerals and Mineral
Names of the International Mineralogical Association.
Type material, totalling about 15 mg of gysinite on the
sample, is preserved in the Department of Mineralogy at
the Geneva Natural History Museum.
vescencein cold dilute hydrochloric acid. There is no noticeable fluorescenceunder both long- and short-wave
ultraviolet light. It sinks in Clerici's solution. Using the
Gladstone-Dale relationship with revised constants proposed by Mandarino (l98la), K" : 0.1634 and Ko :
0.1654, indicating superior compatibility between the
chemicaland physical data; the calculateddensity is 4.82
g/cm3.The mineralis biaxialnegativewrth 24: 70', indicesof refractiond : 1.745,P: 1.805,y : 1.840(all+0.005)
with a perceptibler < u dispersion.24* : 72.4".The optical orientation is X : c, Y : a, Z : b.
X-ray crystallography
X-ray single-crystalstudy by the Weissenbergmethod
shows that gysinite is orthorhombic with space group
Pmcn as confirmed by the determination of the structure
Physical and optical properties
(Chabot et al., 1985).The unit-cell parameters,correspondGysinite is translucent,light pink to reddish pink in ing to the meansof measurements
from singlecrystal films,
color,with a vitreousto greasyluster;the streakis white to
a r ea : 5 . M , b : 8 . 5 0 a n d c : 7 . 2 5 4 . T h e a : b : c r a t i oi s
light pink. The hardnesscould not be measured.In thin O.5929:1:0.8529.
The refinedvalues,obtainedwith a foursection,it is colorlessto light pink. The crystalsare euhe- circle automated diffractometer using MoKa radiation,
dral with a pronouncedpseudo-octahedral
habit, elongated ^: O.7rO7, are a : 5.0028(8), b : 8.555(1), and
along b, and are up to 1 mm in length.The observedforms c:7.2392(81. The refinementis based on 35 reflections
are {lll} and {110}.The mineral,brittle with a lack of (17.451"< 2e < 22.523")using the IARAMprogram (Stewcleavage,occurs as isolated single crystals (Fig. 1), crystal art et al., 1976).The X-ray powder pattern of gysinite has
aggregates(Fig. 2a.)and penetrationtwins (Fig. 2b.)on the been establishedusing both Gandolfi and Guinier-Hiigg
specimen.The twin plane is (100)but it was impossibleto cameraswith CuKc radiation.t: 1.54184.Ni-filteredfor
determine the twin axis. Gvsinite is soluble with effer- the first one. non filtered for the secondone.The valuesin
0003-o04x/85/1
I I 2-13t4$02.00
SARP AND BERTRAND: GYSINITE
Table l. X-ray powder diffraction data of gysinite and ancylite
(P.D.F. card 29-384)
A n c y li t e
G y si n i t e
d..r.(8) dobs(8)
Fig. l. Pseudooctahedral single crystal of gysinite with the
position of the main optical elements.
Table I are from the 114.6mm diameterGandolfi camera.
with Z : 2 and a molecular weight of 450.7(basedon the
method describedby Mandarino, 1981b,the calculated
densityis 4.82 glcm3.In Table 1, powder diffractiondata
for gysinite and ancylite, (RE)-(Ca,Sr)2--(CO3)2(OH),'
(2 - x)HrO (P.D.F. card 29-384)are presented.The comparisonof d-spacingand visual intensityvaluesshowsthe
structural similarity betweenthesetwo minerals.
Chemical composition
Gysinite was chemicallyanalyzedwith a lnr urvrx-sumicroprobeequippedwith four wavelengthspectrometersand
a Tracor-Northern energy dispersivesystem.Wavelength
scansmade with Pb stearate.RAP. ADP and LiF analyzing crystals,and long counting periods with the energy
0ll
Ir0
021
012
102
022
031
200
122
l3l
013
2?0
040
z2l
2l?
123
l4l
033
004
133
?13
104
6
5.51
4.335
3-667
3.334
2.943
2.758
2.639
2.520
2.4?0
2 . 3 3 81
2 . 3 2 5|
?.168
2.t25
2.077
2.010
1.939
1. 8 9 0
t.839
1.813
1.727
1 . 7 0 9,
1 . 7 0 6I
Ivis
5.54
4.3?5
3.676
3.336
2.950
2.76?
2.640
2.522
2.431
) 11A
50
100
r00
40
50
2.171
2 .I 3 0
?.074
?.021
|.941
1. 9 0 0
1.840
1.814
1.734
t'tv>
plus about l5 weaklines
a
tlrt
30
l5
5.57
4.34
3.71
3.36
2.96
2.78
2.66
2.53
2.44
s0
100
100
40
100
20
40
40
20
50
2.35
80
<5
l0
25
l5
20
2.18
2.15
2.O9
2.0?
1.953
1.908
I .855
1.829
1.743
l0
30
70
70
s0
l0
30
30
30
l5
1.718
20
q
)
60
50
pl us rcre than
?0 veak I ines
1 1 4 . 6m r G a n d o l f i c a r e r d , C u ( a r a d i a t i o n , f l i - f i l t e r e d
dispersive system showed the presenceof Pb, La, Nd and
C. No other rare-earth elements were detected' The presence of water, confirmed by thermogravimetric analysis,
was suggested by the behavior of gysinite under the beam.
Profiles across the mineral showed slight variations in the
Fig. 2. Somehabits of gysinite(a) Aggregateof crystals.(b) Two crystalsassociatedby a penetrationtwin. SEM photomicrographs;
scalebar is -0.2 mm.
S A R PA N D B E R T R A N D :G Y S I N I T E
Table 2. Microprobe analysesof gysinite
Variabi I i ty t+
range
wtX
Mean +f
41o.;6 fft
proportions
Pb0
?6.5 - 31.0
29.1
0.59
Pb
ltd203
3s.0- 43.0
4,0- 7.5
1 7 . 4- 2 2 . 3
38.9
| .04
lid
1a203
co2
'?ot
fota I
I
rr
tit
5.6 -
5.8
2 0 .I
6.5
6.1
0.t5
LA
2.05
c
3.03
H
t0b.00
uy drtterence
Eased on 2l analyses
6n gh" basis of 6 oxygen atoms
distribution of elements but without any evidence of a particular zonation. For quantitative analyses,the instrument
was operated at 20 kV and 50 nA (measured on benitoite)
and counting was stopped by a constant digitized beamcurrent. The following natural and synthetic standards
were used: PbCO3 for Pb and C, and two glasses of
Li2B4Oj, with 5 wt.% Nd2O3 andLarO, respectively,for
Nd and La. Gysinite and the standards were coated with
Ni. The beam was slightly defocussed to minimize the instability of the glasses and gysinite. The instrumental and
matrix effects were corrected using a ZAF program
(ulctc). The results are given in Table 2. The amount of
CO2 + HrO determined by thermogravimetry on 10 mg of
gysinite using a Mettler T.A.l instrument is about 23 wt.o/..
This is in rather good agreement with the probe-measured
CO, content and the HrO content obtained by difference.
The validity of the chemical analysis has been confirmed
by the structure determination (Chabot et al., 1985). The
empirical formula calculated on the basis of 8 oxygen
atoms is: Pbo.5e(Nd1.o4,Lao.rr)"r.,r(CO3)2.os(OH)o
.ur. 1.2
HrO
or, ideally, P(Nd,La)(COJ2(OH).H2O
with
Nd > La, which corresponds to the Pb-Nd analog of ancylite.
Paragenesis
Gysinite is associated with malachite, cerussite, talcchlorite, bornite, wulfenite, kasolite, native gold, garnet and
schuilingite (Piret et al,1982; Sarp et al., 1983).
As proposed for schuilingite (Piret et al., 1982), the rareearth elements in gysinite possibly originated from the
trace elements in uraninite of the Shaba ore deposits. Monazite, which is also associated with secondary copper and
uranium minerals in the oxidation zone of these deposits, is
not affected by alteration processes.
Nomenclatureand structure
Dal Negro et al. (1975) determined the crystal structure
of ancylite and proposed the general formula (RE),(Ca,
Sr)r-,(CO.),(OH),.(2 - x)HrO. Depending upon the
value of the Sr/Ca ratio, two varieties were defined: a
strontian ancylite and a calcian ancylite. Sawyer et al.
(1973) synthesized RE(OH)CO.; this isostructural compound represents the end-member composition of ancylite-
Therefore, on the basis of the
type structure with x:2.
two known chemical compositions of the ancylitecalcioancylite series and the known composition of the
phase synthesized by Sawyer et al. (1973), one can consider
ideal
two
end-members: (RE)r(CO.)r(OH),
and
(REXMXCO3),(OH)'HrO, with the M site occupied by divalent cations. Extending the solid-solution beyond the
point M/RE : 1.0, there exists, for x:0,
the potential
compound (Ca, Sr)r(CO3)2'2H2O, or more generally
(Ca,Sr[COr)'HrO. Natural Ca{CO3)'HrO occurs as the
mineral monohydrocalcite; it is not isotypic with the ancylite series (Effenberger, 1981). The Sr-analogue, Sr(CO.)'
HrO, has not yet been found.
As (RE)2(CO3)z(OH)2,for x:2, and (RE[M[CO3)'(OH)
'HrO, for x : l, are isostructural and becausethe divalent
cations are missing in (RE)r(COr)z(OH)2, it is apparent
that the divalent cations have no signiflcant influence on
the bond connectivity of ancylite-type structures. For
x: 1, divalent cations are present in the structure and
ancylite, calcioancylite and gysinite, may be considered as
end-members of a Seriesof solid solutions with the general
formula: (RE),(M)2-"(CO3)2(OH),'(2 - x)HrO. The formulas of these three mineral species are: (Sro.oo,
Cao.r r)rr.ur(Ceo."r, La o.,u)E1.3E(CO3)2(OH)r..,' 0.62 H 20,
for ancylite (Dal Negro et al., 1975), Cao.6r(Ceo.rr,
Lao.r.)r r. r.(CO3)2(OH) r.oe. 0.9 H20, for calcioancylite (Palache et al., 1951, p. 291\ and Pbo.5e(Nd1.o4,
' 1.2 HtO,for gysinite.
Lao.rr)r, 1e(CO3)2.os(OH)o.u.
gysinite
is the Pb--Nd equivalent of ancylite.
Chemically
From a structural point of view, it has a great similarity to
ancylite: space group and cell parameters are very close
and the estimated intensities of diffraction lines in the two
powder patterns are also in good agreement. Thus gysinite
is isostructural with ancylite (Dal Negro et al., 1975).
Acknowledgments
We are greatly indebted to Dr. A. Kato, previous chairman of
the International Commission on New Minerals and Mineral
Names,for his critical and useful comments,to Dr. P. Tissot of
the Department of Analytical and Technical Chemistry of the
University of Geneva for the thermogravimetricmeasurements
and to Drs. J. Grice, F. C. Hawthorne and A. Robertsfor critically
reviewingthe manuscript.We also wish to thank Mrs. J. Berthoud
for typing the manuscriptand Dr. J. Wiiest of the GenevaNatural
History Museum for the SEM photomicrograpbsof gysinite.
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June 18,l9E4:
Matwscriptreceiued,
accepteilfor publication,Iune I 8, I 985.