Geographic Origin Determination of Paraiba Tourmaline

Full text

Minerals of the tourmaline supergroup are cy-
closilicates with the general formula
XY3Z6(T6 )(BO3)3V3W, where X = (Na+, O18
Ca2+, K+, and vacancy); Y = (Fe2+, Mg2+, Mn2+, Cu2+, Al3+
,
Li+, Fe3+
, and Cr3+); Z = (Al3+, Fe3+, Mg2+, and Cr3+); T =
(Si4+, Al3+, and B3+); B = (B3+); V = (OH–and O2–), and W
= (OH–, F–, and O2–) (e.g., Henry et al., 2011). Tourma-
line-supergroup minerals can be classified into three
primary groups based on the X-site occupancy: the al-
kali group (Na+ and K+ dominant), the calcic group
(Ca2+ dominant), and the X-site vacant group (vacancy
dominant). In each primarytourmaline group, specific
species are further determined based on theoccupancy
of other sites. Thirty-four species have been recog-
nized by the InternationalMineralogicalAssociation’s
Commission on New Minerals, Nomenclature and
Classification (IMA-CNMNC; e.g.,Henry et al.,2011;
Hawthorne and Dirlam, 2011; B. Dutrow, pers.
comm., 2017). Elbaite is a sodium-, lithium-, and alu-
minum-rich species in the alkali group, with the gen-
eral formula (Na)(Li1.5 )Al6Si6 (BO3(OH)3(OH). Al1.5 O18 )3
Liddicoatite is a calcium- and lithium-rich species
in the calcic group, with the general formula
(Ca)(Li2Al)Al6Si6 (BO3)3(OH)3(OH). Most gem-qual-O18
ity tourmaline has been reported as elbaite. Liddi-
coatite was first distinguished as a separate mineral
species in 1977 (Dunn et al., 1977). Gem-quality lid-
dicoatite tourmaline from Madagascar has been
prized for its remarkable color zoning that is typically
characterized by triangular zones and three-rayed
stars surrounded by oscillatory zonings when it is cut
perpendicular to the c-axis (e.g., Dirlam et al., 2002;
Pezzotta and Laurs, 2011).
Cuprian (copper-bearing) tourmalines with vivid
blue, green-blue, green, and violet colors were first
reported in 1989 from Paraíba State in northeastern
Brazil (Koivula and Kammerling, 1989). They are
now commonly called “Paraíba” or “Paraíba-type”
tourmaline in the trade. Fritsch et al. (1990) and Bank
et al. (1990) reported that the blue to green colors
were primarily due to the presence of trace (or minor)
amounts of copper. Years after the initial discovery
in the state of Paraíba, similar gem-quality elbaite
tourmalines colored by copper and manganese were
found elsewhere in Brazil (Shigley et al., 2001; Fu-
ruya, 2007), in Nigeria (Smith et al., 2001), and in
Mozambique (Abduriyim and Kitawaki, 2005; Laurs
et al., 2008). The composition of cuprian tourmaline
from all of these deposits has been determined with
energy-dispersive X-ray fluorescence spectrometry
(EDXRF), electron microprobe analysis, and laser ab-
lation–inductively coupled plasma–mass spec-
troscopy (LA-ICP-MS; see Abduriyim et al., 2006;
Okrusch et al., 2016). No mineral species other than
elbaite has been previously reported for “Paraíba”
tourmalines except for four pieces of Cu-bearing lid-
dicoatite first reported by Karampelas and Klemm
(2010) showing Ca-rich X-site occupancy and three
CUPRIAN LIDDICOATITE TOURMALINE
Yusuke Katsurada and Ziyin Sun
FEATURE AR ICLES
Cuprian (copper-bearing) tourmaline, known as “Paraíba” tourmaline in the trade, has been an important
gem since its discovery in 1989. Until now, almost all of the material reported has been classified as the
elbaite species of the tourmaline supergroup. Chemical analyses by laser ablation–inductively coupled
plasma–mass spectroscopy (LA-ICP-MS), a common technique for origin determination of Paraíba tour-
malines, revealed that 13 copper-bearing samples submitted to GIA’s Tokyo laboratory contained sub-
stantial amounts of Ca in the X-site. Consequently, they are classified as liddicoatite tourmaline. The
origin of these stones is unknown.
See end of article for About the Authors and Acknowledgments.
GEMS & GEMOLOGY, Vol. 53, No. 1, pp. 34–41,
http://dx.doi.org/10.5741/GEMS.53.1.34
© 2017 Gemological Institute of America
34 CUPRIAN LIDDICOATITE TOURMALINE GEMS & GEMOLOGY SPRING 2017

In Brief
• Almost all copper-bearing tourmaline has been classi-
fied as the elbaite species. Cuprian liddicoatite exists,
however, and may have entered the “Paraíba” tourma-
line market.
• Only sophisticated quantitative chemical analysis can
effectively separate liddicoatite from elbaite.
• Cuprian liddicoatite shows high Ga and high Pb.
Under long-wave UV, it displays stronger fluorescence
than cuprian elbaite due to high concentrations of rare
earth elements.
Figure 1. Six of the 13
cuprian liddicoatite
tourmalines from this
study. The faceted
stones weigh 1.59–9.63
ct (average 3.95 ct).
They are transparent
and have greenish blue,
green-blue, and green
colors. Photos by Ma-
sumi Saito.
CUPRIAN LIDDICOATITE TOURMALINE GEMS & GEMOLOGY SPRING 2017 35
pieces of possible liddicoatite conjectured from the
qualitative analysis indicating high Ca (Leelawatana-
suk and Jakkawanvibul, 2011). This article reports
on the same type of cuprian tourmalines that belong
to the liddicoatite species based on the evidence sup-
ported by quantitative analysis.
MATERIALS AND METHODS
Thirteen tourmaline samples of Paraíba-type colors
(figure 1) from unknown geographic origins were ex-
amined in GIA’s Tokyo laboratory. These were sub-
mitted by different clients in 2016. Standard
gemological testing was followed by analyses of the
major, minor, and trace element concentration for
each sample with LA-ICP-MS. Fluorine was not meas-
ured. A Thermo Fisher Scientific’s iCAP Qc ICP-MS
was connected to an Electro Scientific Industries
NWR213 laser ablation unit with a frequency-quintu-
pled Nd:YAG laser (213 nm wavelength) running at 4
ns pulse width. NIST SRM 610 and 612 glass stan-
dards were used for external calibration. Ablation was
achieved using a 40 μm diameter laser spot size, a flu-
ence (energy density) of approximately 10 J/cm2, and
a 7 Hz repetition rate.Three laser spots were acquired
from the girdle of each sample. The composition was
initially internally standardized with 29Si using a cal-
culated amount of Si based on the weight percent of
pure elbaite in the chemical formula. Twenty-six ad-
ditional cuprian tourmaline samples submitted by
clients were analyzed with LA-ICP-MS for compari-
son. Their geographical origin was identified using
GIA’s tourmaline database. Eighteen of these addi-
tional samples were from Brazil, one from Nigeria, and
seven from Mozambique.
The data was converted to wt.% oxides and nor-
malized to 100 wt.% and then converted back to
ppmw to obtain individual element concentrations,
based on 27 O2– and 4 OH–anions per formula. LA-
ICP-MS analysis for tourmaline is an incomplete char-
acterization, with critical lightelements (H and F) and

TABLE 1. Chemical composition of 13 cuprian tourmaline samples, obtained by LA-ICP-MS.
Sample CT1 CT2 CT3 CT4 CT5 CT6 CT7 CT8 CT9 CT10 CT11 CT12 CT13
no
ppmw
atoms per formula unit, 27 O + 4 OH anions normalization
X-site
Y-site
Z-site
B-site
T-site
Detection limits (ppmw) are: Li (0.95–1.31), B (8.78–10.42), Na (18.91–19.34), Al (3.41–3.48), Ca (339–364), Mn (0.55), and Cu (0.42–0.45). Si is
used as internal standard.
Sum
36 CUPRIAN LIDDICOATITE TOURMALINE GEMS & GEMOLOGY SPRING 2017
Li 11,600 11,700 12,300 13,600 12,300 12,800 12,500 13,000 13,900 11,700 12,100 12,600 15,300
B 33,900 34,400 33,200 35,200 32,500 34,700 35,200 31,500 33,600 34,400 37,600 34,100 40,300
Na 8920 8480 8050 8390 8960 7600 9130 9860 8170 7910 7120 8220 7810
Al 220000 218,000 230,000 220,000 224,000 217,000 218,000 228,000 225,000 217,000 216,000 222,000 197,000
Si 169,000 169,000 158,000 163,000 166,000 169,000 161,000 164,000 161,000 168,000 164,000 166,000 171,000
Ca 21,000 21,300 24,100 24,400 21,800 21,700 22,800 20,400 23,500 22,200 20,800 22,800 20,400
Mn2+ 2160 3110 5780 3610 3480 3340 12,300 2130 3480 6530 8000 2860 10,100
Cu 1490 1610 2120 1510 2140 1600 2790 1550 1460 2300 2510 1330 2970
X site 0.14 0.15 0.09 0.08 0.11 0.17 0.08 0.11 0.10 0.15 0.22 0.12 0.20
vacancy
Ca 0.50 0.50 0.57 0.58 0.52 0.51 0.54 0.48 0.56 0.52 0.49 0.54 0.48
Na 0.37 0.35 0.33 0.35 0.37 0.31 0.38 0.41 0.34 0.33 0.29 0.34 0.32
X-site 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
total
Al 1.42 1.36 1.46 1.22 1.49 1.30 1.15 1.59 1.37 1.31 1.08 1.37 0.63
Cu 0.02 0.02 0.03 0.02 0.03 0.02 0.04 0.02 0.02 0.03 0.04 0.02 0.04
Li 1.58 1.60 1.70 1.86 1.68 1.74 1.72 1.79 1.90 1.60 1.65 1.73 2.08
Mn2+ 0.04 0.05 0.10 0.06 0.06 0.06 0.21 0.04 0.06 0.11 0.14 0.05 0.17
Y-site 3.06 3.04 3.29 3.16 3.26 3.12 3.13 3.44 3.36 3.06 2.91 3.17 2.92
total
Al 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00
Z-site 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00
total
B 2.97 3.01 2.92 3.08 2.85 3.04 3.10 2.77 2.95 3.02 3.29 2.99 3.50
B-site 2.97 3.01 2.92 3.08 2.85 3.04 3.10 2.77 2.95 3.02 3.29 2.99 3.50
total
Si 5.70 5.71 5.35 5.50 5.62 5.68 5.46 5.55 5.46 5.67 5.53 5.58 5.74
Al 0.30 0.29 0.65 0.50 0.38 0.32 0.54 0.45 0.54 0.33 0.47 0.42 0.26
T-site 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00
total
Cation 18.89 18.90 19.12 19.17 19.01 18.99 19.15 19.10 19.20 18.93 18.98 19.03 19.22
sum
Anion 31.00 31.00 31.00 31.00 31.00 31.00 31.00 31.00 31.00 31.00 31.00 31.00 31.00
sum

•
•
•
•
• 0
0
•
Figure 2. A: The 13 cuprian tourmaline samples belong to the calcic group, while the 26 additional cuprian tour-
malines belong to the alkali group based on the dominant occupancy of X-site. B: Li, Y-site Fe2+, and Y-site Mg2+
distinguish the tourmaline species as liddicoatite in a liddicoatite-feruvite-uvite subsystem ternary diagram. C: Li,
Y-site Fe2+
, and Y-site Mg2+ of elbaite samples were further plotted in a dravite-schorl-elbaite subsystem ternary di-
agram (modified after Henry et al., 2011).
A: Primary tourmaline groups - X-site B: Liddicoatite-feruvite-uvite subsystem C: Dravite-schorl-elbaite subsystem
Ca2+ 1.5Li+ 2Li+
0.00 1.00
Liddicoatite
Feruvite Uvite
0.00 1.00
Elbaite
Schorl Dravite
1.00
0.00
0.50 0.50 0.50 0.50 0.50 0.50
1.00 0.00 1.00 0.00 1.00 0.00
Calcic
group
X-vacant
group
Alkali
group
0.00 0.50 1.00 0.00 0.50 1.00 0.00 0.50 1.00
X-site vacancy Na+(+K+) Y-site Fe2+ Y-site Mg2+ Y-site Fe2+ Y-site Mg2+
Cuprian liddicoatite tourmaline Cuprian liddicoatite tourmaline Cuprian elbaite tourmaline from Brazil
Cuprian elbaite tourmaline from Brazil Cuprian elbaite tourmaline from Mozambique
Cuprian elbaite tourmaline from Mozambique Cuprian elbaite tourmaline from Nigeria
Cuprian elbaite tourmaline from Nigeria
CUPRIAN LIDDICOATITE TOURMALINE GEMS & GEMOLOGY SPRING 2017 37
theoxidation statesof transition elements (Fe and Mn)
undetermined.In thisarticle,it is assumedthat Fe and
Mn are divalent, that the B-site is fully occupied by B,
and that the X-site is occupied by Na, Ca, and a va-
cancy equal to 1 atom per formula unit (apfu). Addi-
tional assumptions are that the Z-site is only occupied
by Al3+ and equal to 6 apfu, while the T-site is occupied
by Si4+ and Al3+ and equal to 6 apfu. If Si4+ is greater
than 6, the T-site is only occupied by Si4+
. The excess
Al goes into the Y-site. The priority of ions with dif-
ferent valence states entering the Y-site is (R2+ > R3+ >
R+> R4+), such that the Y-site is occupied by Mn, Cu,
Al, and Li. The common assumption that all iron is
ferrous and that OH + F = 4 apfu can result in the
misidentification of buergerite as “fluor-schorl” as
well as misidentificationof the oxy-andfluor-species.
The chemical composition presented in this article is
not affected by the minor amounts of Fe in the tour-
maline (Clark, 2007). The assumption of 4 OH–does
not allow for the fluor- or oxy- species to be deter-
mined. The major elements, including Ca, Na, Si, Al,
and Mg, were verified by comparison of LA-ICP-MS
data with electron microprobe data of a secondary
tourmaline standard with similar Ca:Na ratios
(Dutrow and Henry, pers. comm., 2017).
RESULTS AND DISCUSSIONS
Microscopic examination of the 13 samples revealed
two-phase inclusions, needle-like growth tubes, and
fluid inclusions typical of tourmaline. Standard
gemological testing resulted in the general range of
gem tourmalines such as refractive indices of 1.62–
1.64 and specific gravity of approximately 3.06, but
the fluorescence under long-wave ultraviolet light
was stronger than the usual Paraíba tourmalines, as
described later. Chemical analysis demonstrated a
calcium-dominant composition. The representative
data in table 1 was selected to show the best stoi-
chiometry. All the data points showed liddicoatite,
and none were classified as elbaite. In all analyses,
Mg was below the detection limit and Fe was less
than 0.005 apfu. Based on the primary tourmaline
group classification, all 13 calcium-rich cuprian sam-
ples are classified as calcic-group tourmaline and the
26 additional sodium-rich cuprian samples as alkali-
group tourmaline (table 2, figure 2A). In addition, the
13 calcic-group samples plot as liddicoatite tourma-
line in a liddicoatite-feruvite-uvite subsystem ter-
nary diagram (figure 2B). The 26 tourmalines in the
alkali group are shown as elbaite in a dravite-schorl-
elbaite subsystem ternary diagram (figure 2C; Henry
et al., 2011).
Comparing the data in table 1 with that of liddi-
coatitic tourmaline from Madagascar (Dirlam et al.,
2002) shows that these cuprian samples have more
sodium in the X-site—with a greater elbaitic compo-
nent. Other liddicoatite tourmalines from Canada
(Teertstra et al., 1999) have similar sodium (0.365–

•
•
•
•
•
• . ,
., .);,' .
••
• •
• •
• •••
TABLE 2. X-site occupancy of 26 cuprian elbaite samples in molecular proportions, obtained by LA-ICP-MS.
Na K Ca Vacancy
Brazil
Mozambique
Nigeria
0.395 apfu) and similar or lower calcium (0.420–0.498
apfu). The sodium contents of liddicoatite from
Madagascar and Canada vary with their zonation.
Table 3 shows the samples’ averaged chemical
composition for selected minor and trace elements.
In cuprian tourmalines from different origins, these
have some distinguishable trends (Abduriyim et al.,
2006; Okrusch et al., 2016). For example, Brazilian
and Nigerian cuprian tourmalines tend to show
higher concentrations of Cu than those from
Mozambique—which typically have higher Ga than
the other two sources. Nigerian stones tend to have
higher Pb than those from Brazil and Mozambique.
Figure 3 shows the Ga-Pb distribution of the 13
cuprian liddicoatite and 26 cuprian elbaite samples
analyzed in this study. The cuprian liddicoatite sam-
ples show both high Ga (297–433 ppmw) and high Pb
(420–827 ppmw). These combinations of trace ele-
ments plot well outside the ranges of any known ref-
erence samples in GIA’s database, and therefore their
geographic origin could not be determined.
Another remarkable point was the samples’ high
concentration of rare earth elements (REE; table 2)—
in other words, lanthanides except Pm. Lighter REE
(La, Ce, Pr, Nd, Sm, and Gd) showed a higher con-
centration than heavier REE (Tb, Dy, Ho, Er, Tm, Yb,
and Lu). The samples show an exceptionally low Eu
content. The high concentration of REEs is inter-
preted as the cause of their comparatively strong flu-
orescence under long-wave UV (figure 4).
Although the geographic origin of these cuprian
liddicoatite is unknown, this unique chemical prop-
erty offers directions for further research. Geological
studies of the elbaitic cuprian tourmaline deposits in
Brazil have been published (e.g., Shigley et al., 2001;
Soares et al., 2008; Beurlen et al., 2011), but no de-
tailed study has been carried out for Nigerian and
Mozambican occurrences. Teertstra et al. (1999) re-
ported that some liddicoatite crystals have cores that
correspond to elbaite with rims of liddicoatite. They
proposed three possibilities for the calcium needed
to form liddicoatite: mobilization of Ca from earlier-
formed pegmatite minerals, introduction of Ca from
host rocks, and conservation of Ca through the crys-
tallization of minerals in the pegmatite magma.
Major elements can also be used to determine prove-
nance. Henry and Guidotti (1985) established distinct
regions to define potential different source rock types
of tourmaline using Al-Fe(tot)-Mg and Ca-Fe(tot)-Mg
ternary diagrams. Figure 5 indicates that the rock
Pb (ppmw)
P
Pb-Ga CONCENTRATION
1300 Cuprian liddicoatite tourmaline
urmaline
1200 Cuprian elbaite tourmaline fr
om Brazil aline fr
1100 Cuprian elbaite tourmaline fr
aline from Mozambique
Cuprian elbaite tourma
aline fr
om Nigeria
1000
900
800
700
600
500
400
300
200
100
0
0
200 400
600
Ga (ppmw)
Figure 3. Pb vs. Ga con-
centration plot of the 13
cuprian liddicoatites of
unknown origin and 26
cuprian elbaite tourma-
lines from Brazil,
Mozambique, and Nige-
ria. The 13 cuprian lid-
dicoatites have high Pb
and high Ga. Cuprian
elbaite tourmalines
from Brazil have low Pb
and low Ga. Cuprian
elbaites from Mozam-
bique have high Ga and
low Pb, while those
from Nigeria have low
Ga and high Pb.
38 CUPRIAN LIDDICOATITE TOURMALINE GEMS & GEMOLOGY SPRING 2017
0.705 (0.513–0.861) 0.003 (0.001–0.005) 0.063 (0.000–0.112) 0.229 (0.073–0.381)
0.596 (0.519–0.661) 0.002 (0.002–0.003) 0.057 (0.025–0.131) 0.346 (0.205–0.444)
0.724 (0.699–0.748) 0.003 (0.003–0.003) 0.111 (0.103–0.116) 0.162 (0.145–0.185)

TABLE 3. Minor and trace element concentration (ppmw) of 13 cuprian liddicoatite samples and
26 cuprian elbaites from Brazil, Mozambique, and Nigeria.
CT1 CT2 CT3 CT4 CT5 CT6 CT7 CT8 CT9 CT10 CT11 CT12 CT13 Brazil
(18 samples) Mozambique
(7 samples)
bdl 1.90 bdl bdl bdl bdl bdl bdl bdl bdl bdl bdl 0.25
2220 3140 5740 3570 3510 3440 12300 2130 3430 6490 7900 2790 9820
bdl 261 72.4 66.0 34.9 20.0 208 bdl 36.0 155 241 42.9 201
1530 1580 2100 1490 2140 1650 2850 1560 1530 2250 2550 1220 2860
397 373 333 368 382 375 297 433 359 324 319 376 349
4.99 17.0 76.9 42.6 27.9 42.2 108 4.28 42.8 87.3 99.9 27.5 93.2
20.3 54.2 230 131 88.1 131 316 20.0 137 277 304 92.0 319
4.89 9.62 31.2 18.9 15.5 19.6 40.5 5.06 19.8 32.6 39.9 11.8 39.5
36.5 47.1 111 76 72.2 71.9 126 37.3 72.4 115 123 65.0 120
40.0 29.5 27.0 26.7 58.3 26.6 26.0 45.7 27.8 25.6 28.8 23.0 28.0
1.26 0.79 0.63 0.64 1.57 0.75 0.64 1.64 0.73 0.77 0.71 0.69 0.71
12.2 8.25 7.65 6.84 15.1 6.43 7.59 13.3 7.48 7.15 8.22 6.44 6.71
0.89 0.51 0.43 0.40 1.18 0.41 0.48 0.86 0.39 0.45 0.51 0.34 0.46
1.48 1.00 0.82 0.66 1.67 0.79 0.79 1.44 0.71 0.77 0.92 0.84 0.75
0.08 0.06 0.04 0.04 0.07 0.05 0.05 0.10 0.05 0.05 0.06 0.03 0.06
0.09 0.09 0.10 0.06 0.10 0.13 0.09 0.07 0.10 0.09 0.09 0.07 0.08
bdl 0.00 0.01 0.01 0.00 0.01 0.00 0.01 bdl 0.00 bdl 0.00 0.01
0.08 0.05 0.02 bdl 0.05 0.04 bdl 0.07 0.03 0.01 bdl 0.05 bdl
0.01 bdl 0.01 0.00 bdl bdl 0.01 0.01 bdl bdl bdl 0.00 bdl
7.31 6.52 5.30 7.18 5.06 6.85 4.18 8.05 7.92 6.53 6.70 7.70 5.83
703 672 550 773 659 774 420 761 827 642 578 567 684
123 168 486 304 282 300 626 130 309 547 606 228 609
Mg
Mn2+
Fe2+
Cu
Ga
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Ta
Pb
∑REE
112
(0–1170)
11800
(420–26300)
164
(0–1060)
9580
(420–23200)
139
(61.2–232)
0.69
(bdl–3.72)
0.97
(bdl–5.79)
0.07
(bdl–0.42)
0.12
(bdl–0.82)
0.02
(bdl–0.13)
0.00
(bdl–0.01)
0.01
(bdl–0.06)
0.00
(bdl–0.01)
0.00
(bdl–0.01)
0.00
(bdl–0.00)
0.00
(bdl–0.00)
0.00
(bdl–0.01)
0.00
(bdl–0.01)
0.02
(bdl–0.40)
2.23
(0.04–8.35)
44.4
(2.74–188)
1.89
bdl
4360
(99.5–12100)
bdl
2310
(1140–3430)
321
(255–401)
0.01
(bdl–0.03)
0.02
(bdl–0.06)
0.00
(bdl–0.00)
bdl
bdl
bdl
0.00
(bdl–0.02)
bdl
bdl
0.00
(bdl–0.00)
0.00
(bdl–0.01)
0.00
(bdl–0.00)
0.00
(bdl–0.01)
bdl
1.58
(0.54–3.62)
43.9
(3.85–123)
0.03
Nigeria
(1 sample)
0.73
18700
209
2470
143
0.04
0.04
0
bdl
bdl
bdl
bdl
0
bdl
bdl
bdl
bdl
bdl
bdl
6.66
467
0.1
Sample
Abbreviation: bdl = below detection limit. Detection limits (ppmw) are: Mg (0.13–0.56), Mn (0.16–1.01), Fe (6.70–34.02), Cu (0.73–3.00), Ga (0.05–0.19),
La (0.00–1.26), Ce (0.00–0.01), Pr (0.00–0.02), Nd (0.00–0.23), Sm (0.00–0.04), Eu (0.00–0.01), Gd (0.00–0.02), Tb (0.00–0.01), Dy (0.00–0.02), Ho
(0.00), Er (0.00–0.01). Tm (0.00 –0.01), Yb (0.01–0.02), Lu (0.00–0.01), Ta (0.00), and Pb (0.05–0.14).
types in which the cuprian liddicoatite was found are dominant, they must be from a Ca-rich host rock.
Li-rich granitoid pegmatites and aplites. Because Karampelas and Klemm (2010) noted that liddicoat-
these copper-bearing liddicoatite tourmalines are Ca- ite rough had been found near the Paraíba-type el-
CUPRIAN LIDDICOATITE TOURMALINE GEMS & GEMOLOGY SPRING 2017 39

• •
Figure 4. Randomly selected samples under daylight-equivalent light (left) and under long-wave UV light (right).
Copper-bearing liddicoatite (CT05, CT03, and CT06 at the top) show stronger fluorescence than the cuprian
elbaite (MZ04, MZ06, NG01, BR15, BR17, and BR08 at the middle and bottom) due to high REE concentrations.
Photos by Yusuke Katsurada.
Figure 5. A: This Al-Fe(tot)-Mg diagram (in molecular proportions) reveals that the likely source rock of cuprian lid-
dicoatite tourmaline is Li-rich granitoid pegmatite and aplite. Fe(tot) represents the total Fe. This diagram is di-
vided into regions that define the compositional range of tourmaline from different rock types (modified after Henry
and Guidotti, 1985). B: The Ca-Fe(tot)-Mg diagram (also in molecular proportions) shows that the likely source rock
of cuprian liddicoatite tourmaline is Li-rich granitoid pegmatite and aplite. The rock types defined by the fields in
this diagram (also modified after Henry and Guidotti, 1985) are somewhat different from those in figure 5A.
A: Al-Fe(tot)-Mg diagram for tourmaline from B: Ca-Fe(tot)-Mg diagram for tourmaline from
various source rock types various source rock types
Al Ca
Elbaite Liddicoatite
1
2
3 6
8
7
4
5
Uvite
Alkali-free dravite
Schorl Dravite
Buergerite
Uvite
Schorl
Buergerite Dravite
1
2
3
6
4
5
Al Fe(tot) Al Mg
50 50 50 50
Cuprian liddicoatite tourmaline
1. Li-rich granitoid pegmatites and aplites
2. Li-poor granitoids and their associated pegmatites and aplites
3. Fe3+-rich quartz-tourmaline rocks (hydrothermally altered granites)
4. Metapelites and metapsammites coexisting with an Al-saturating phase
5. Metapelites and metapsammites not coexisting with an Al-saturating phase
6. Fe3+-rich quartz-tourmaline rocks, calc-silicate rocks, and metapelites
7. Low-Ca-metaultramaÿcs and Cr, V-rich metasediments
8. Metacarbonates and meta-pyroxenites
Fe(tot) Mg
Cuprian liddicoatite tourmaline
1. Li-rich granitoid pegmatites and aplites
2. Li-poor granitoids and their associated pegmatites and aplites
3. Ca-rich metapelites, metapsammites, and calc-silicate rocks
4. Ca-poor metapelites, metapsammites, and quartz-tourmaline rocks
5. Metacarbonates
6. Metaultramaÿcs
40 CUPRIAN LIDDICOATITE TOURMALINE GEMS & GEMOLOGY SPRING 2017
baite mine in Mozambique. Qualitative EDXRF reportedly near Nampula, Mozambique, showed a
analysis of Paraíba-type tourmaline from a new mine Ca peak (Leelawatanasuk and Jakkawanvibul, 2011).

Analysis of the host rock geology around cuprian
tourmaline mines in Mozambique may be an impor-
tant approach.
CONCLUSIONS
Thirteen cuprian tourmaline samples were identi-
fied as liddicoatite tourmaline. Their Cu and Mn
concentrations were within the range of other
cuprian tourmalines—consistent with their similar
blue to green colors. Except for their stronger fluo-
rescence under long-wave UV, presumably caused
by high REE concentrations, the samples’ gemolog-
ical properties were also similar to cuprian elbaite
tourmalines. Only sophisticated quantitative chem-
ical analyses can effectively separate liddicoatite
from elbaite.
Cuprian liddicoatite tourmaline is not well
known, but the material may have already entered
the “Paraíba” tourmaline market. Discovering its
origin could provide new insights into the geologic
growth conditions and chemical variations of tour-
maline crystals.
ABOUT THE AUTHORS
Dr. Katsurada is a scientist and a staff gemologist at GIA in
Tokyo. Mr. Sun is a staff gemologist at GIA in Carlsbad,
California.
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We wish to thank Dr. Makoto Miura and Takuya Sunaoshi of GIA’s
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appreciate the helpful comments and suggestions from Shane
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State University.
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