Mineralogical Magazine, June 2014, Vol. 78(3), pp. 747–755

Torrecillasite, Na(As,Sb)3+
4 O6Cl, a new mineral from theTorrecillas mine, Iquique Province, Chile: description andcrystal structure
A. R. KAMPF1,*, B. P. NASH2, M. DINI3 AND A. A. MOLINA DONOSO4
1

Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los
Angeles, CA 90007, USA
2
Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
3
Pasaje San Agustin 4045, La Serena, Chile
4
Los Algarrobos 2986, Iquique, Chile[Received 1 January 2014; Accepted 27 February 2014; Associate Editor: G. Della Ventura]
ABSTRACTThe new mineral torrecillasite (IMA2013-112), Na(As,Sb)3+
4 O6Cl, was found at the Torrecillas mine,
Iquique Province, Chile, where it occurs as a secondary alteration phase in association with anhydrite,
cinnabar, gypsum, halite, lavendulan, magnesiokoritnigite, marcasite, quartz, pyrite, scorodite,wendwilsonite and other potentially new As-bearing minerals. Torrecillasite occurs as thin colourlessprisms up to 0.4 mm long in jack-straw aggregates, as very thin ﬁbres in puff balls and as massiveintergrowths of needles. Prisms are elongated on [100] with diamond-shaped cross-section andirregular terminations. Crystals are transparent, with adamantine lustre and white streak. The Mohs
hardness is 2, tenacity is brittle and fracture is irregular. Cleavage on (001) is likely. The calculated
density is 4.056 g cm 3. Optically, torrecillasite is biaxial ( ) with a = 1.800(5), b = 1.96(1), g =2.03(calc.) (measured in white light). The measured 2V is 62.1(5)º, no dispersion or pleochroism wereobserved, the optical orientation is X = c, Y = b, Z = a. The mineral is very slowly soluble in H2O,
slowly soluble in dilute HCl and rapidly soluble in concentrated HCl. The empirical formula,determined from electron-microprobe analyses, is (Na1.03Mg0.02)S1.05(As3.39Sb0.62)S4.01O6.07Cl0.93.
Torrecillasite is orthorhombic, Pmcn, a = 5.2580(9), b = 8.0620(13), c = 18.654(3) Å, V = 790.7(2) Å3
and Z = 4. The eight strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 4.298(33)(111),
4.031(78)(014,020), 3.035(100)(024,122), 2.853(39)(115,123), 2.642(84)(124,200), 2.426(34)(125),
1.8963(32)(225) and 1.8026(29)(0·1·10,233). The structure, reﬁned to R1 = 4.06% for 814 Fo >4sF
reﬂections, contains a neutral, wavy As2O3 layer parallel to (001) consisting of As3+O3 pyramids thatshare O atoms to form six-membered rings. Successive layers are ﬂipped relative to one another andsuccessive interlayer regions contain alternately either Na or Cl atoms. Torrecillasite is isostructural
with synthetic orthorhombic NaAs4O6Br.
K EY WORDS : torrecillasite, new mineral, arsenite, crystal structure, Torrecillas mine, Chile.

Introduction
THE Torrecillas mine, in the northern Atacama
Desert of Chile, is a small, long-inactive As mine

* E-mail: akampf@nhm.org
DOI: 10.1180/minmag.2014.078.3.20# 2014 The Mineralogical Society

consisting of several small pits and a shaft on
Torrecillas Hill, overlooking the Paciﬁc Ocean.
The deposit was probably discovered and ﬁrst
mined during the guano mining boom of the early
19th century. During that period, the Peruvian
Government owned and claimed several guanoﬁelds along the Chilean coast in the Iquique andA. R. KAMPF ET AL.

The rare secondary chlorides, arsenates andarsenites have been found at three main sites on
the hill: an upper pit measuring ~8 m long and
3 m deep, a lower pit ~100 m from the upper pit
and measuring ~5 m long and 3 m deep and amine shaft adjacent to the lower pit and lower on
the hill. The torrecillasite was ﬁrst found by oneof the authors (AAMD) in early 2012 in boulders
on the hill slope just below the mine shaft and hecollected additional material there in mid-2013.
The boulders appear to represent the oxidation
cap of the deposit.
Torrecillasite is associated with anhydrite,
cinnabar, gypsum, halite, lavendulan, magnesiokoritnigite (Kampf et al., 2013a), marcasite,
quartz, pyrite, scorodite and wendwilsonite.
Leverettite (Kampf et al., 2013b), canutite(Kampf et al., 2014) and several other potentially
new arsenate and arsenite minerals, currently
under study, have also been found at the locality.
The secondary assemblages at the Torrecillas
deposit are interpreted as having formed from theTarapacá provinces, including the proliﬁc
Huanillos, Chanabaya and Pabellón de Picadeposits, which are not far from the Torrecillasarea (Mortimer et al., 1971). The guano mines
under Peruvian administration, were exploited
mainly by English companies. Torrecillas mine
was probably abandoned several years prior to1950 (Pimentel, 1978).
The new mineral torrecillasite, described herein
and named for the locality, is the fourth newmineral species described from the mine. The
discoveries of all four new species [the others
being leverettite (Kampf et al., 2013b), magnesiokoritnigite (Kampf et al., 2013a) and canutite(Kampf et al., 2014)] and several others, yet to be
described, are the result of recent ﬁeld investigations and collecting at the locality by one of theauthors (AAMD). An image of the locality isprovided by Kampf et al. (2013a) and appears on
the cover of the December 2013 issue of
Mineralogical Magazine.
The new mineral and the name have been
approved by the International Mineralogical
Association (IMA2013-112). The description isbased upon four cotype specimens that are
deposited in the collections of the Natural
History Museum of Los Angeles County, 900
Exposition Boulevard, Los Angeles, CA 90007,
USA, catalogue numbers 64079, 64080, 64081
and 64082.
Occurrence
The Torrecillas mine is located on Torrecillas
Hill, Iquique Province, Tarapacá Region, Chile(~20º58’13’’S 70º8’17’’W). Four different rockunits are exposed on the hill. Rocks of the
Coastal Range Batholith (mainly gabbros)
extend from the seashore to the Pan-American
Road along the base of the hill. At the foot of thehill is a small area of contact metamorphic rocks
in which garnet crystals occur in metamorphosed
shales. Higher on the hill, rocks are predominantly andesites and porphyritic lavas of theJurassic La Negra Formation. The Torrecillas
deposit, which the Torrecillas mine exploits,
consists of two main veins rich in secondary As
and Cu minerals that intersect metamorphosed
marine shales and lavas. These veins are related
genetically to the above-mentioned andesites andporphyritic lavas of the La Negra Formation.
More information on the geology and mineralogy of the area is provided by Gutiérrez(1975).

FIG. 1. Backscatter scanning electron microscope imageof torrecillasite crystals.

748

TORRECILLASITE, A NEW MINERAL FROM IQUIQUE, CHILETABLE 1. Electron microprobe analyses of torrecillasite
Constituent

Wt.%

Na2O
MgO
As2O3
Sb2O3
Cl
O=Cl
Total

6.56
0.15
68.64
18.43
6.75
1.52
99.01

Range
6.07
0.12
65.40
15.66
6.37

7.04
0.18
71.85
20.72
7.24

Utah using a Cameca SX-50 electron microprobewith four wavelength-dispersive spectrometers.
Analytical conditions were 15 kV accelerating
voltage, 10 nA beam current and a beam diameterof 10 mm. Counting times were 20 s on peak and
10 s on + and background. No other elements
were detected by energy dispersive spectroscopy.
Other possible elements were sought by electron
microprobe analysis, but none was above thedetection limit. Raw X-ray intensities werecorrected for matrix effects with a f(rz)algorithm (Pouchou and Pichoir, 1991). The
standards used were albite for Na, diopside forMg, synthetic GaAs for As, synthetic GaSb for Sb
and tugtupite for Cl. Analytical data are given in
Table 1. The ranges for the As and Sb analyses
reﬂect Sb substitution for As, as is also indicatedby the crystal structure reﬁnement (see below).
The empirical formula based on O + Cl = 7 is(Na1.03Mg0.02)S1.05(As3.39Sb0.62)S4.01O6.07Cl0.93.
The simpliﬁed structural formula is NaAs3+
4 O6Cl,which requires Na2O 6.82, As2O5 87.13, Cl 7.81,
O = Cl 1.76, total 100 wt.%. The GladstoneDale compatibility index 1 (KP/KC) is 0.012 forthe empirical formula, in the range of superior
compatibility (Mandarino, 2007).

SD
0.36
0.02
2.37
2.14
0.36

oxidation of native As and other As-bearing
primary phases, followed by later alteration bysaline ﬂuids derived from evaporating meteoric
water under hyperarid conditions (e.g. Cameron etal., 2007).
Physical and optical properties
Torrecillasite occurs as thin colourless prisms up to
0.4 mm long in jack-straw aggregates (Fig. 1), asvery thin ﬁbres in puff balls and as massiveintergrowths of needles. Prisms are elongated on[100] with diamond-shaped cross-section andirregular terminations. Crystals are transparent,with adamantine lustre and white streak. The Mohs
hardness is 2 based on scratch tests. The tenacity
is brittle and the fracture is irregular. Cleavage was
not observed, but is likely on (001) based on the
crystal structure. The density could not bemeasured because there is insufﬁcient material
for direct measurement and crystals are nearlyinvisible in Clerici solution. The mineral is very
slowly soluble in H2O (hours), slowly soluble indilute HCl (minutes) and rapidly soluble inconcentrated HCl (seconds).
The calculated density is 4.056 g cm 3 basedon the empirical formula. Optically, torrecillasite
is biaxial ( ) with a = 1.800(5), b = 1.96(1), g =2.03(calc.) (measured in white light). The 2V
measured from extinction data using EXCALIBR(Gunter et al., 2004) is 62.1(5)º. Because liquids
with index of refraction >2 were unavailable, g
was calculated from a, b and 2V. No dispersion
was observed and torrecillasite is nonpleochroic.
The optical orientation is X = c, Y = b, Z = a.

X-ray crystallography and structure
reﬁnement

Composition
Quantitative analyses (six points over four
crystals) were performed at the University of
749

Both powder and single-crystal X-ray studies
were carried out using a Rigaku R-Axis Rapid II
curved imaging plate microdiffractometer, withmonochromatic MoKa radiation. For the powderdiffraction study a Gandolﬁ-like motion on the jand o axes was used to randomize the sample andobserved d spacings and intensities were derived
by proﬁle ﬁtting using JADE 2010 software(Materials Data, Inc.). The powder data presented
in Table 2 show good agreement with the patterncalculated from the structure determination. Unitcell parameters reﬁned from the powder datausing JADE 2010 with whole-pattern ﬁtting are a= 5.2677(9), b = 8.0412(15), c = 18.626(3) Å andV = 789.0(2) Å3.
The Rigaku CrystalClear software package wasused for processing structure data, including theapplication of both numerical and empiricalabsorption corrections, the latter being a multiscan correction using ABSCOR (Higashi, 2001).
The structure was solved by direct methods using
SIR2004 (Burla et al., 2005), after which thecoordinates were transformed to conform withthose reported for synthetic NaAs4O6Br (Pertlik,

A. R. KAMPF ET AL.

TABLE 2. Powder X-ray data for torrecillasite*.
Iobs

dobs

dcalc

Icalc

hkl

27

4.654

4.66354.58034.28634.03684.03103.98253.94013.7002
3.59393.38583.20203.15303.10903.04963.02602.84672.84472.73812.67622.63802.62902.53992.53042.46682.42852.39292.37352.33182.31782.29022.28002.23322.22302.20302.07652.06072.0075
1.9912

38
3
62
100
14
3
10
8
27
6
13
33
6
8
49
15
18
19
57
43
56
5
4
5
22
11
34
3
11
5
4
9
5
18
11
11
8
3

0 0 4
1 0 2
1 1 1
0 1 4
0 2 0
1 1 2
0 2 1
0 2 2
1 1 3
0 1 5
1 1 4
1 2 1
0 0 6
0 2 4
1 2 2
1 1 5
1 2 3
0 2 5
1 0 6
1 2 4
2 0 0
1 1 6
2 0 2
0 3 3
1 2 5
1 3 0
1 3 1
0 0 8
1 3 2
2 0 4
1 1 7
1 3 3
0 2 7
2 1 4
2 1 5
1 1 8
2 0 6
2 2 4

33

4.298

78

4.031

24
3

3.597
3.398

23

3.168

{

{

10

{
2.853 {
2.707 {
2.642 {
2.544 {

34

2.426

24

2.377

19

2.315

100
39
21
84

18
11
11

3.035

2.213

{

{
2.0045 {2.0696

Iobs

dobs

7

1.953432

1.893629

1.80262

1.748911

1.7144{14

1.6765{27

1.6003{22

1.5593{16

1.5266{27

1.4972{25

1.4656{14

1.3689{10

1.342216

1.3179

{

dcalc

Icalc

hkl

1.97001.94801.9173
1.8964
1.8725
1.84481.8174
1.79891.74451.71771.7055
1.6975
1.67841.67001.61001.60751.6014
1.5955
1.58881.58401.57651.56081.5562
1.53581.52681.5196
1.4983
1.49501.47611.46451.46351.3803
1.37141.35981.3421
1.32751.32491.3145

3
10
4
22
7
3
11
14
3
5
5
4
4
9
3
12
4
7
6
6
3
6
4
7
9
7
15
16
4
5
11
3
12
9
10
3
3
10

0 4 2
2 1 6
0 4 3
2 2 5
1 4 1
1 4 2
0·1·102 3 3
2 0 8
1·1·10
3 1 1
2 2 7
2 3 5
1 3 8
1 4 6
0 4 7
3 2 1
2 1 9
0 5 2
3 2 2
2 4 2
0 5 3
3 2 3
2 3 7
3 0 6
3 2 4
1·2·112·1·10
3 2 5
1 4 8
3 3 1
3 1 8
2 4 7
2 5 2
2 5 3
3 3 6
1·4·104 0 0* Only calculated lines with intensities 53 are shown.

1987), with which torrecillasite is isostructural.
SHELXL-2013 (Sheldrick, 2008) was used for thereﬁnement of the structure.
The occupancies of the four independent As
sites were reﬁned with joint occupancies by As
and Sb. The As2 and As3 sites reﬁned to fulloccupancy by only As, while the As1 site reﬁned
to 0.586(10) As and 0.414(10) Sb and the As4 site
reﬁned to 0.930(9) As and 0.070(9) Sb. As acrosscheck, the occupancies of the As sites werealso analysed using the program OccQP (Wright750

et al. 2001), which uses quadratic equations in aconstrained least-squares formulation to optimize
occupancy assignments based upon site scattering, chemical composition, charge balance,bond valence and cation-anion bond lengths.
OccQP calculations with the number of As andSb atoms per formula unit set to correspond to the
EPMA results provided the following occupancies: As1: (As0.564Sb0.436), As2: (As0.977Sb0.023),
As3: (As0.953Sb0.047), As4: (As0.887Sb0.113). Our
ﬁnal reﬁnement is based upon the aforementioned

TORRECILLASITE, A NEW MINERAL FROM IQUIQUE, CHILETABLE 3. Data collection and structure-reﬁnement details for torrecillasite.
Diffractometer
X-ray radiation/power
Temperature
Structural FormulaSpace group
Unit-cell dimensions

Rigaku R-Axis Rapid II
MoKa (l = 0.71075 Å)/50 kV, 40 mA
298(2) K
Na(As3.38Sb0.62)S4.00O6Cl
Pmcn
a = 5.2580(9) Å
b = 8.0620(13) Å
c = 18.654(3) Å
V = 790.7(2) Å3
4
4.058 g cm 3
16.631 mm 1876.614061565
3.34 to 27.46º
6 4 h 4 5, 10 4 k 4 10, 23 4 l 4 224605/1000; Rint = 0.062
814
99.4%
Full-matrix least-squares on F2
69
1.198
R1 = 0.0406, wR2 = 0.0667
R1 = 0.0561, wR2 = 0.0703+1.141/ 1.254 e A 3

Z
Density (for above formula)
Absorption coefficientF(000)
Crystal size (mm)y range
Index ranges
Reflections collected/unique
Reflections with Fo >4s(F)Completeness to y = 27.46º
Refinement method
Parameters refined
GoF
Final R indices [Fo >4s(F)]R indices (all data)
Largest diff. peak/hole

Rint = S|F2o F2o(mean)|/S[F2o]. GoF = S = {S[w(F2o F2c )2]/(n p)}1/2. R1 = S||Fo| |Fc||/S|Fo|.
wR2 = {S[w(F2o F2c )2]/S[w(F2o)2]}1/2; w = 1/[s2(F2o) + (aP)2 + bP]
where a is 0, b is 5.406 and P is [2F2c + Max(F2o,0)]/3.

reﬁned site occupancies, rather than thosecomputed using OccQP.
Data collection and reﬁnement details are given
in Table 3, atom coordinates and displacement
parameters in Table 4, selected bond distances inTable 5 and a bond-valence analysis in Table 6.
Description of the structure
The structure of torrecillasite (Fig. 2) contains aneutral, wavy As2O3 layer parallel to (001)consisting of As3+O3 pyramids that share O
atoms to form six-membered rings. Successive
layers are ﬂipped relative to one another andsuccessive interlayer regions contain alternately
either Na or Cl atoms. The Na and Cl nestle aboveand below the centres of half of the six-memberedrings in each As2O3 layer. Besides the three short
As O3 bonds, which deﬁne the As3+O3 pyramids,
the As3+ cations also form much longer bonds to
Cl atoms in the interlayer region and/or to O atoms
in the same As 2 O 3 layer. This is typical751

coordination geometry for As3+ due to its lonepair electrons. Na is coordinated to 8 O atoms (6 inthe As2O3 layer to which it is closest and 2 in thenext As2O3 layer) and to one Cl atom, with the
Na Cl bond extending through the centre of a sixmembered ring in the As2O3 layer. The short
As O bonds within the As2O3 layer are muchstronger than the other bonds in the structure,especially the very long As O bonds, suggesting
the likelihood of a perfect (001) cleavage.
As noted above, torrecillasite is isostructural
with the orthorhombic synthetic phase
NaAs4O6Br (Pertlik, 1987). Other compoundswith the general formula MAs4O6X (M = K,
NH4; X = Cl, Br, I) were reported by Pertlik(1988) to be hexagonal and to possess planar
As2O3 sheets with interlayer regions containing M
cations alternating with interlayer regions
containing halogen atoms. The recently describedmineral lucabindiite, (K,NH 4 )As 4 O 6 (Cl,Br),(Garavelli et al., 2013; IMA2011-010) is isostructural with the latter compounds.

0.4002(5)0.16859(10)0.65653(12)0.41702(12)0.78414(12)0.9400(8)0.3831(8)0.6680(5)0.1930(6)0.4904(3)

¯˘
¯˘
¯˘
¯˘
¯˘
¯˘

0.0010(9)0.9978(10)¯˘
0.5588(2)0.87893(5)0.04509(6)0.18118(5)0.82924(5)0.8994(4)0.8607(3)0.8745(2)0.9519(2)0.71233(15)z/c0.0318(10)0.0241(3)0.0227(3)0.0197(3)0.0212(3)0.0254(16)0.0253(16)0.0239(11)0.0301(12)0.0350(7)Ueq
0.033(3)0.0188(5)0.0180(5)0.0160(5)0.0157(5)0.029(4)0.030(4)0.018(2)0.027(3)0.0286(14)

U11

752

1.882(7)1.894(5)3.165(4)3.446(2)2.699

2.497(6)2.602(6)2.715(6)2.761(2)2.956(5)2.678

As1 O1As1 O4 (62)
As1 O2 (62)
As1 Cl (62)<As1 j>Na O4 (62)
Na O3 (62)
Na O4 (62)
Na O1 (62)Na Cl
<Na j>Na
As4 (62)
As4As3As3 (62)
As1 (62)

As2 O2As2 O4 (62)
As2 O3 (62)<As2 j>
Cl
Cl
Cl
Cl
Cl
Cl

0.035(2)0.0250(5)0.0216(5)0.0211(5)0.0223(5)0.023(3)0.020(3)0.029(3)0.036(3)0.0367(15)U220.028(2)0.0285(5)0.0285(6)0.0220(5)0.0257(6)0.025(4)0.026(4)0.025(2)0.027(3)0.0397(15)U33

2.956(5)3.206(2)3.219(3)3.336(3)3.379(2)3.446(2)1.785(6)1.798(5)3.287(4)2.391

As3 O2As3 O3 (62)
As3 ClAs3 Cl (62)<As3 j>1.791(6)1.806(4)3.336(3)3.379(2)2.583

TABLE 5. Selected bond distances (Å) for torrecillasite.

* Reﬁned site occupancies: As1: As/Sb = 0.586/0.414(10); As4: As/Sb = 0.930/0.070(9).

Na
As1*
As2
As3
As4*
O1
O2
O3
O4
Cl

y/b

x/a

U23
0
0
0
0
0
0
0
0.003(2)0.003(2)0U13

As4 O1As4 O3 (62)
As4 Cl (62)
As4 Cl<As4 j>0.0014(19)0.0022(4)0.0019(4)0.0004(4)0.0030(4)0.002(3)0.003(3)0.001(2)0.005(2)0.0118(12)TABLE 4. Atom coordinates and displacement parameters (Å2) for torrecillasite.

1.814(7)1.826(5)3.206(2)3.219(3)
2.516

0
0
0
0
0
0
0
0.003(2)0.011(2)0U12

A. R. KAMPF ET AL.

TORRECILLASITE, A NEW MINERAL FROM IQUIQUE, CHILETABLE 6. Bond-valence analysis for torrecillasite. Values are expressed in valence units (vu).
O1
Na

0.075 62;?

As1
As2

0.911

As3
As4

0.959

Sa

2.020

O2

O3

O4

0.115 62?

0.153 62?

0.041 62;?
1.011

0.017 62?

0.884 62?
0.976 62?

0.995

0.955 62?
0.929 62?

2.088

2.016

2.098

Cl
0.113
0.085 62?
0.040 62;?
0.042
0.037 62;?
0.062 62;?
0.060
0.493

Sc
0.969
2.841
2.997
3.021
3.001

Multiplicities indicated by 6;?; bond strengths based on assigned site occupancies; Na+ O and As3+ O bondstrengths from Brown and Altermatt (1985); As3+ Cl bond strengths from Brese and O’Keeffe (1991); Sb3+ O
bond strengths from Mills et al. (2009).

FIG. 2. The structures of torrecillasite and lucabindiite. Upper: structures viewed with c axis vertical and a axis
approximately towards the observer; middle: As2O3 sheets viewed on edge (c axis vertical). Lower: As2O3 sheets
viewed along c axis. As atoms in red, O atoms in white, large cations (Na, K, NH4) atoms in blue and halide (Cl, Br)atoms in green. Short As O bonds are shown as red sticks, long As O bonds as thin black lines and (Na,K,NH4) O
bonds as white sticks. Unit-cell outlines are shown as thick black lines.

753

A. R. KAMPF ET AL.

The As2O3 layers in all of these compounds
consist of AsO3 pyramids that share O atoms toform six-membered rings. Besides the obvious
geometric difference between the two types oflayers (wavy for the orthorhombic MAs4O6X
phases and planar for the hexagonal MAs4O6X
phases), the layers also differ topologically. In theplanar layer, all of the As apices point in the same
direction, while in the wavy layer, one of the four
As apices (As2) points in the opposite direction.
The structures and layers of torrecillasite andlucabindiite are compared in Fig. 2.
The bond-valence analysis (Table 6) exhibits
one striking anomaly. The bond-valence sum(BVS) for the Cl site is 0.493 vu. Interestingly, it
is noteworthy that very low BVS values are found
for the Br site in NaAs4O6Br (0.657 vu) and the
Cl site (Cl0.5Br0.3F0.2) in lucabindiite (0.309 vu).
The very low BVS values for the X sites in thesestructures are probably related to the strong
repulsive effects of the As3+ lone-pair electrons,
which are directed into the interlayer spacesurrounding the X sites.
Finally, a comment about the joint As/Sb
occupancies in the As sites of the torrecillasite
structure seems warranted. Given the similar
stereochemistry of As3+ and Sb3+ (with a relatively
small difference in radius), the articulating natureof the As/Sb layer and the weak layer-to-layer
connectivity through a soft Cl sandwich, there
appears to be no obvious restraint on the extent of
Sb substitution. The Sb-ordering preferenceindicated, i.e. As1 > As4 > As3 = As2, very
probably helps to reduce strain within the As/Sb
layer, in conjunction with the connectivity to theﬂanking Na atoms. An all-Sb 3+ analogue,
NaSb4O6Cl, appears possible and would clearly
warrant separate species status. With increasing Sb
content, toward the mid-point in a hypothetical
NaAs4O6Cl NaSb4O6Cl series, an intermediatephase with Sb dominating the As1 site is likely toexist and one with Sb dominating both the As1 andAs4 sites may exist; however, we do notrecommend that such intermediate phases be
granted separate species status; i.e. we recommendthat separate species status only be afforded to aphase in which total Sb is greater than total As.
Acknowledgements
Reviewers Mark Cooper and Anna Garavelli arethanked for their constructive comments on the
manuscript. A portion of this study was funded by
the John Jago Trelawney Endowment to theMineral Sciences Department of the Natural
History Museum of Los Angeles County.
References
Brese, N.E. and O’Keeffe, M. (1991) Bond-valence
parameters for solids. Acta Crystallographica, B47,
192 197.
Brown, I.D. and Altermatt, D. (1985) Bond-valence
parameters from a systematic analysis of the
inorganic crystal structure database. Acta
Crystallographica, B41, 244 247.
Burla, M.C., Caliandro, R., Camalli, M., Carrozzini, B.,
Cascarano, G.L., De Caro, L., Giacovazzo, C.,
Polidori, G. and Spagna, R. (2005) SIR2004: an
improved tool for crystal structure determination andreﬁnement. Journal of Applied Crystallography, 38,381 388.
Cameron, E.M., Leybourne, M.I. and Palacios, C. (2007)
Atacamite in the oxide zone of copper deposits innorthern Chile: involvement of deep formationwaters? Mineralium Deposita, 42, 205 218.
Garavelli, A., Mitolo, D., Pinto, D. and Vurro, F. (2013)
Lucabindiite, (K,NH4)As4O6(Cl,Br), a new fumarole
mineral from the ‘‘La Fossa’’ crater at Vulcano,Aeolian Islands, Italy. American Mineralogist, 98,
470 477.
Gunter, M.E., Bandli, B.R., Bloss, F.D., Evans, S.H., Su,
S.C. and Weaver, R. (2004) Results from a McCrone
spindle stage short course, a new version of
EXCALIBR, and how to build a spindle stage. The
Microscope, 52, 23 39.
Gutiérrez, H. (1975) Informe sobre una rápida visita ala mina de arsénico nativo, Torrecillas. Instituto deInvestigaciones Geológicas, Iquique, Chile.
Higashi, T. (2001) ABSCOR. Rigaku Corporation,
Tokyo.
Kampf, A.R., Nash, B.P., Dini, M. and Molina Donoso,
A.A. (2013a) Magnesiokoritnigite,
Mg(AsO3OH)·H2O, from the Torrecillas mine,
Iquique Province, Chile: the Mg-analogue ofkoritni gite. Mineralogical Magazine, 77,
3081 3092.
Kampf, A.R., Sciberras, M.J., Williams, P.A., Dini, M.
and Molina Donoso, A.A. (2013b) Leverettite fromthe Torrecillas mine, Iquique Provence, Chile: theCo-analogue of herbertsmithite Mineralogical
Magazine, 77, 3047 3054.
Kampf, A.R., Mills, S.J., Hatert, F., Nash, B.P., Dini, M.
and Molina Donoso, A.A. (2014) Canutite,
NaMn3[AsO 4] 2[AsO 2(OH)2 ], a new protonatedalluaudite-group mineral from the Torrecillas mine,
Iquique Province, Chile. Mineralogical Magazine,
78, (in press).
Mandarino, J.A. (2007) The Gladstone-Dale compatibility of minerals and its use in selecting mineral754

TORRECILLASITE, A NEW MINERAL FROM IQUIQUE, CHILE

species for further study. The Canadian
Mineralogist, 45, 1307 1324.
Mills, S.J., Christy, A.G., Chen, E.C.-C. and Raudsepp,
M. (2009) Revised values of the bond valence
parameters for [6]Sb(V) O and [3 11]Sb(III) O.
Zeitschrift für Kristallographie, 224, 423 431.
Mortimer, C., Saric, N. and Cáceres, R. (1971) Apuntes
sobre algunas minas de la región costera de laprovincia de Tarapacá. Instituto de Investigaciones
Geológicas, Santiago de Chile, Chile.
Pimentel, F. (1978) Proyecto Arsenico Torrecillas.
Instituto de Investigaciones Geológicas, Iquique,
Chile.
Pertlik, F. (1987) The crystal structure of NaAs4O6Br.
Journal of Solid State Chemistry, 70, 225 228.

Pertlik, F. (1988) The compounds KAs4O6X (X = Cl, Br,I) and NH4As4O6X (X = Br, I): hydrothermal
syntheses and structure determinations. Monatsheftefür Chemie, 119, 451 456.
Pouchou, J.-L. and Pichoir, F. (1991) Quantitative
analysis of homogeneous or stratiﬁed microvolumes
applying the model "PAP". Pp. 3l 75 in: Electron
Probe Quantitation (K.F.J. Heinrich and D.E.
Newbury, editors). Plenum Press, New York.
Sheldrick, G.M. (2008) A short history of SHELX. Acta
Crystallographica, A64, 112 122.
Wright, S.E., Foley, J.A. and Hughes, J.M. (2001)
Optimization of site occupancies in minerals using
quadratic programming. American Mineralogist, 85,
524 531.

755