Minrecordite
a new mineral from Tsumebby Carlo G. Garavelli and Filippo Vurro
Instituto di Mineralogia e Petrografia
University of Bari, Piazza Umberto
70121 Bari, Italy

ABSTRACT
Minrecordite is the Ca and Zn member of the dolomite series,
Cazn(COlh, with an ordered arrangement of cations and belonging to space group R3. It was found on a unique dioptase specimen
from Tsumeb, Namibia, which came from the second oxidation
zone, presumably at the 30-32 level. The mineral forms minute,twisted, pearly, lustrous rhombohedrons up to about 0.5 mm. Theygrew following a first generation of large dioptase crystals, andbefore a second generation characterized by more minute andmorphologically complex individuals.
Two distinct variants of minrecordite have been identified. TypeA represents nearly pure Cazn(COlh. with only a minor substitution of Mg, Fe, and Mn for Zn. It has a = 4.8183(4), c =16.0295(l0)A. Measured specific gravity is 3.45(2); calculated density is 3.445 g/cm'. The indices of refraction are w = 1.750(2), E =1.550(2). Type B is a magnesian variety. Its unit-cell parameters arelarger; specific gravity and indices of refraction are lower. Its
deposition is apparently earlier than that of pure minrecordite.
On several dioptase druses from Tsumeb a mineral occurs, quite
similar in appearance to minrecordite, and occupying the same
position in the paragenetic sequence. This mineral can be easily
confused visually with minrecordite itself, but analyses show it to
be merely a zincian variety of dolomite.
The mineral and its name were approved by the I.M.A. Commission in February 1981. It is named from Mineralogical Record, aworthy magazine in promoting both a better knowledge of Tsumeb
minerals and a more beneficial interaction between professional
and amateur mineralogists. The holotype specimen of minrecordite
is in the Museum of the Institute of Mineralogy, Bari (Italy)
University.
INTRODUCTION
In 1967 one of us (G. Fioravanti) obtained in exchange, from a
Johannesburg collector, several specimens of crystallized dioptase
from Tsumeb. One specimen, about 5 x 5 x 6 ern, exhibited, scattered on dioptase, a number of microcrystals of a white mineral.
These were provisionally labeled 'willemite," perhaps on the basisof its high Zn content as revealed by some qualitative chemical
tests.
Some years later, a more accurate re-examination of this specimen showed that the white mineral forms very small, strongly
twisted rhombohedral crystals, quite dissimilar in their morphology
from any known willemite crystals. Moreover, the occurrence of
The Mineralogical Record, May-June,

1982

and Gian Carlo Fioravanti
Gruppo Mineralogico Romano
2 Via Monterone
00186 Rome, Italy

younger willemite on dioptase seemed in disagreement with theparagenetic sequences of Tsumeb secondary minerals, as describedby Keller (1977). For these reasons, the specimen was submitted tothe attention of the Institute of Mineralogy of Bari University, inorder to establish the true identity of the minute white crystals.
As a result of this detailed study, we became convinced that wewere dealing with a new mineral species, of ideal composition
CaZn(COlh, corresponding to a new member of the dolomite
series. For this new mineral we have proposed the name min recordite. This name is in honor of the magazine the Mineralogical
Record, which is especially worthy as an active promoter of a betterknowledge of Tsumeb minerals. Moreover, this mineral has beenfound as a result of collaboration between professional mineralogists and a collector. Thus the name seems particularly appropriate
owing to the worldwide success of the Mineralogical Record in
bridging the gap between professional and amateur mineralogists.
The new mineral and its name were approved by the I.M.A.
Commission on New Minerals and Mineral Names in February
1981.

1. A moderately twisted, milky whitemosaic rhombohedron of minrecordite measuring 0.075 mm on edge. Fioravanti specimen.
Figure131

Table 1. Indexed powder patterns for minrecordite(Diffractometer,
Cu K, filtered radiation, step-scanning
at 0.01 2t? steps and 2.10" fixed counts).
0

MagnesianMinrecordite

Figure 2. A milky white cluster of minrecordite
about 0.7 mm across at the base. A dioptase (II)crystal is perched on the cluster, and a darker
cluster of magnesian minrecordite is present
behind and to the right. Fioravanti specimen.

The original minrecordite-bearing
single specimen was subsequently divided into several fragments (only three of which still exist) for mineralogical studies. A piece (designated as the holotype) is
now deposited in the mineral collection of the Institute of Mineralogy of Bari University, numbered HO-4/81. Cotypes are in theprivate collections of G. Fioravanti (Rome) and C. L. Garavelli(Bari).
DESCRIPTION
and PARAGENESIS
The matrix of the minrecordite-bearing
specimen is reddish,massive and partly earthy or ocherous. It has the well-known appearance of dioptase specimens from the second Tsumeb oxidation
zone, at the 30-32 levels; the only distinctive feature is the complete
lack of country rock (gray dolostone) usually present in the matrixof dioptase druses from Tsumeb. The reddish matrix is rich in small
masses and veins of milky white crystals, mostly anhedral and only
occasionally (on the inside of small vugs) in the form of well-shaped
minute rhombs. These crystals are a zincian variety of dolomite,admixed with spathic calcite. As a rule, they include or are partly
coated with very fine-grained, light green duftite and much smaller
amounts of malachite needles. A thin layer of this material can also
be observed between the matrix and the large dioptase crystals.
The malachite crystals range from about 10 to 15 mrn in length.
They are lustrous, semitransparent,
dark emerald-green, and are
partly strewn with minute minrecordite crystals.
Minrecordite occurs as two variants which are visually distinguishable from each other:Type A (generally referred to here simply as minrecordite or"pure" rninrecordite, with the understanding that "pure" is used as arelative term): Rhombohedral microcrystals up to about 0.5 mrn,
which are very markedly saddle-shaped, milky white in color andwith a typical very strong pearly luster.
Type B (generally referred to here as "magnesian" minrecordite):
More regular and less twisted rhombohedral
microcrystals. As arule, they are almost completely transparent, glassy and colorless;typically they nest at the bases of small hemispherical aggregates,
which are composed principally of pure minrecordite (but see addendum).
Magnesian minrecordite crystals are smaller (0.2 mm as the maximum rhomb edge) and by far scarcer than pure minrecordite. They
typically include a very fine-grained, reddish ocherous pigment; occasionally they are intimately admixed with cerussite and calcite.
As will be shown below, these two minrecordite variants differ

132

1

(A)

h

k

1
0
1
0
0
1
1
0
2
0
0
1
2
1
2
2
1
1
0
0

1 4.0380
1 2 3.7012
0 4 2.8903
0 6 2.6716
1 5 2.5422
2.40911
1 3 2.1962
2
1 2.0689
0 2 2.0191
2 4 1.8506
1 8 1.8062
1 6 1.7891
1 1 ·1.5696
2 2 1.5475
1 4 1.4676
8 1.4452
0
1 9 1.4322
2 5 1.4152
1.39093
0 12 1.33579

oodeale.

dobs.

(A)

4.039
3.70082.88962.67232.54182.40952.19652.06852.01921.85061.8064
1.78891.5696
1.5475
1.46751.4452
1.4322
1.4152
1.39091.33575

I
10
20
100
3
3
25
20
3
15
10
33
40
5
8
10
3
3
2
5
3

Minrecordite(A)I

3.71712.90593.71802.905620100

2.55692.41772.20542.55692.41762.2060< 1

2.02671.85861.81791.7983
1.5752
1.5532
1.47351.45302.0266
1.85781.81801.79901.57571.55331.47351.4528

2
10
35
35
3
10
12
2

1.4212
1.39591.4211
1.39571
5

deale.

(A)

dobs.

20
25

slightly in chemical composition, unit-cell parameters and physicalproperties.
The youngest mineral in this assemblage is represented by a second generation of dioptase, which occurs as very small (always lessthan 1 mrn) individuals of rather complex morphology. They correspond to "dioptase II," according to Keller (1977), while the muchlarger crystals of this mineral, grown before minrecordite,areequivalent to Keller's "dioptase I." In our specimen, the minutedioptase II individuals are emerald-green and completely transparent when perched on magnesian minrecordite. The much larger
number of dioptase II crystals, grown on pure minrecordite, are, asa rule, slightly opalescent, with a distinctive, lighter, bright bluishgreen color. Therefore the paragenetic sequence is as follows:
1. Calcite + zincian dolomite + duftite (also in small veins
within the matrix).
2. Dioptase I, in large euhedral emerald-green crystals.
3. Magnesian rninrecordite, rarely associated with cerussite andcalcite.
4. Minrecordite.
5. Dioptase II, either bluish green or emerald-green in color, asemphasized above.
In many other dioptase specimens from Tsumeb, a mineral wasobserved very similar in appearance to the above-mentioned
minrecordite, both in the pearly luster of the crystals and in their evident saddle-shape. This mineral was shown, however, to be merely
zincian dolomite or, in some cases, nearly pure dolomite; in the latter case the crystals are not markedly twisted. Because of the close
external similarity of this zincian dolomite to minrecordite, some
information about it will be given in a further section.
PHYSICAL and OPTICAL PROPERTIES
TlJeminute minrecordite crystals exhibit, as their only form, the{ 1014} rhombohedron,with markedly twisted and saddle-shaped
faces. Minrecordite is distinguished also by its strong, sometimes
dazzling!.. pearly luster and by the mosaic structure of the crystals.
The {1014} cleavage is prominent.
The Mineralogical Record. May-June.

1982

Mohs hardness is 3.5. Specific gravity, measured by immersion in
Clerici's solution, is 3.45(2) for pure minrecordite and 3.32(2) for
magnesian minrecordite. Calculated density values derived fromunit cell parameters and chemical composition (see below) are 3.445
g/cm- and 3.306 g/cm ' respectively.
Optically, minrecordite is uniaxial negative and strongly birefringent. The indices of refraction (Na light) are:Minrecordite:w = 1.750
E = 1.550
Magnesian minrecordite: w = 1.734
E = 1.542
These values are approximate to ± 0.002 for minrecordite and ±0.003 for magnesian minrecordite. Independent of the experimental
precision, a larger dispersion of the results was noted for the magnesian variety. This may be related to slight compositional differences between individual crystals of this type.
No fluorescence was observed under longwave or shortwave
ultraviolet light.
These results suggest that we are dealing with a trigonal carbonate containing a substantial amount of cations smaller than Ca,
and with either an ordered, less symmetrical, dolomite-like or adisordered, calcite-like structural arrangement of the cations.
X-RAY CRYSTALLOGRAPHY
X-ray single-crystal study would have been desirable in order todetermine the amount of distortion of coordination polyhedra
around the cations. However, this study was impossible due to theinferior quality of the mosaic crystals.
A high-resolution powder diffraction pattern was recorded separately for minrecordite and for its magnesian variety. The stepscanning technique (0.01° 2{) intervals) was adopted, operatingwith high resolution slits on two samples of about 3 mg each. The
examined minerals were spread on the surface of a pure, powdered
and compressed NaF support, allowing the NaF surface to remain
exposed between sample grains. With this preparation technique,the NaF may also be used as a standard. The examined materials
came from a number of different crystal clusters yielding thepowder pattern of pure minrecordite, but from only two clusters
having the pattern of the magnesian variety.
Observed and calculated d(hkl) values are given in Table I. Bothpatterns are satisfactorily indexed in terms of a trigonal unit-cell,
space group R3. Some reflections are present, the indices of which
violate the requirements of the R3 c space group to which calcite
belongs; this indicates that the mineral has an ordered, dolomitelike cation arrangement.
Least-squares calculation on the powder diffraction data resulted
in the following unit-cell parameters:
Minrecorditea= 4.8183(4) Ac
16.0295(10) A
cia

MagnesianMinrecordite

3.3268arh

322.28 A3
6.0240 Aarh

47° 09'Vc

4.8355(4) A
16.1433(12) A

cia

3.3385Varh

326.89,&.3
6.0622 Aarh

47° 01'acentration and, more markedly, with temperature. The mineral iseasily soluble in 2N HCI at 80° C.
The chemical determination of cations was performed by atomic
absorption spectrometry (A.A.S.). Taking into account the physical and optical properties of the mineral, as well as the results of the
X-ray diffractometer study, and because only very small quantities
were available, no direct determination of CO2 was attempted andall the values were calculated as carbonates.
For pure minrecordite, four separate microanalyses were performed, on four different crystal clusters. The results are given in
Table 2. Though the single analyses differ slightly from each other,
the atomic ratio between Ca and the sum of the other metals isalways very close to unity. On the basis of 6 oxygens, the averaged
values yield the formula:Cas 979(ZnO.
917Mgo.067Feo.034Mno.003)(C03)2
or, ideally, CaZn(C03).
For magnesian minrecordite, two microanalyses were performed(Table 3), but only one of these on a well-purified sample. The
results of these analyses yield the formula:
Ca(ZnO.699Mgo.134CaO.090Feo.06SMno.009)(C03h.
Thus, magnesian minrecordite is a compositional variety less rich inZn, and more calcian and magnesian in comparison with pure minrecordite. Its composition easily explains the lower indices of refraction and specific gravity values, and the larger unit-cellparameters, with respect to pure minrecordite.
The second analysis of magnesian minrecordite was performedon crystals not susceptible to hand-purification and greatly contaminated by admixed cerussite and calcite, both recognized (as thesole impurities) optically and by means of X-ray examination.
Therefore the results, also given in Table 3, show a substantial
amount of Pb, and excess Ca when compared with the content re-

These values are consistent with the chemical composition of theanalyzed minrecordites (see below). They follow the linear variation
rules given by Goldsmith and Graf (1958) for unit cell parametersof trigonal carbonates, as a function of their chemical composition.
CHEMISTRY
Minrecordite is very slowly soluble in cold dilute HC!. The_
solubility and accompanying effervescence increase with acid conThe Mineralogical Record, May-June,

1982

Figure 3. Very small, green dioptase (Il) crystals

to 0.25 mm strewn across white rninrecordite
crystal clusters. Fioravanti specimen.
133

Table 2. Chemical analyses of minrecordite

Table 3. Chemical analyses of magnesian minrecordite

Sample I Sample II Sample ill Sample IV Average
CaCOl
ZnCOl
MgCOl
FeCOl
MnCOl
Sum

44.69
51.22
1.99
1.69
0.15
99.74

CaCOl
ZnCOl
MgCOl
FeCOl
MnCOl

0.9984

44.34
50.30
4.33
1.14
0.14
100.250.9973

45.01
50.86
2.08
2.19
0.18
100.320.9988

0.16
99.99

c,..,
.E

0.9426

0.9793

~

43.97
51.56
2.52
1.78

0.9133]0.8850}0.9009}0.9682}0.9167}0.0528 ~ 0.1133 ~ 0.0548 ~ 0.0444 t! 0.0666 ~
0.03260.0217 ::; 0.0420
0.04130.0343 ::;0.00290.00270.00350.00350.0031

§

§

§

II-a

E..,

u
•...

.~
..,

134

III

~o

006988]~~0:1

0.13390.06830.0086

III
46.81
35.84
9.91
6.85
0.59
100.00

3.18
2.20
0.19
100.271.0904

MgCOl
FeCOl
MnCOl

II-b

41.95
41.25
11.50

50.65
40.67
5.24
3.67
0.46
100.69'" CaCOl
",I::
bO

0'"
•...••..
"'><: ZnCOl~\O

ASSOCIATED ZINCIAN DOLOMITESAs pointed out above, a zincian variety of dolomite has been
identified in the small veins of carbonates, occurring within thematrix, or interposed between the matrix and dioptase I crystals. In
these occurrences, zincian dolomite is always admixed with calcite
and duftite, as revealed by optical and X-ray evidence. No otherminerals are present, excepting some malachite needles.
Chemical analyses of these materials were performed by meansof A.A.S. They gave the results quoted in Table 4, sample I (small
veins within the matrix) and II (between matrix and dioptase I).
Owing to the ascertained presence of admixed calcite, the composition of these zincian dolomites cannot be definitely established. On
the assumption of an atomic ratio 1: 1 between Ca and the sum ofsmaller cations, the following formulas are calculated on the basisof 6 oxygens:
Ca(Mgo. 764ZnO.214Mno.00lFeO.OOl)(COlh
Ca(Mgo. 726ZnO.241Feo.028Mno.001)(COl hfor samples I and II respectively.
As mentioned above, and as shown in Table 4, zincian dolomite
and calcite are admixed in these occurrences with duftite andmalachite. Duftite percentages were calculated on the basis ofdetermined Pb contents: the minor amounts of Cu still remaining
were calculated as malachite. No direct determination of As was
carried out, but the presence of this element was qualitatively ascertained.
A third analysis of zincian dolomite was obtained from pearly
white, twisted, rhombohedral crystals occurring on another diop-

PbCOl
CaCOl
ZnCOl
MgCOl
FeCOl
MnCOl
Sum

._

o.~
quired by a dolomite-like formula.
In spite of this, it seems possible to obtain some chemical information by calculating a formula after the subtraction of all the
PbCOl and assuming the atomic ratio between Ca and the sum of
the remaining cations is equal to 1. The formula calculated on thisbasis is:
Ca(Zno.61IMgo.251Feo.i 17Mno.011)(COlh·
Obviously, no definite information is available about the ratio between Ca and the sum of the other metals. It is evident, however,than Zn is dominant among the small cations, though accompanied
by higher amounts of other cations (especially Mg) when comparedwith the formula obtained for magnesian minrecordite in pure crystals.
Among the minor elements, Sr, Pb, Cu, and Co were sought inall the analyzed materials. In pure minrecordite, they were notfound (each less than 10 ppm) with the exception of Cu in analysis
IV (1300 ppm), probably due to a dioptase impurity. In magnesianminrecordite, Sr (85 ppm) and traces of Co (about 20-25 ppm) weredetected. Larger amounts of Sr (160 ppm) are present in the contaminated sample, probably linked with the cerussite or calcite impurities.

Sample II

Sample I

41.85
53.85
1.66
2.12
0.18
99.66

i.oooo

III
III
III
III
III

~
ci

6112
00
]
0.2513 ~0.12650.0110.....;

Note - II-a column: weight percent obtained for a cerussite andcalcite admixed minrecordite.
II-b column: recalculated weight percent after subtractionof all the PbCOl and 26.23 percent CaCOl(excess of CaCOl with respect to a carbonate with 1: 1 ratio between Ca and thesum of other cations).

tase specimen from Tsumeb, and quite similar to minrecordite inappearance.
Unlike samples I and II, this material was very pure, and thus afully reliable formula may be calculated directly from the analyticalresults. On the basis of 6 oxygens, we have:
Ca 1.001(Mgs 894ZnO.05
6Feo.045Mno.004)(COlhwhich corresponds to a far less zincian dolomite.
Traces of Co were detected in all these three zincian dolomites.
Sr is also present; it has a higher concentration (185 ppm) in the lesszincian dolomite.
DISCUSSION
The natural occurrence of a new mineral phase which is structurally a member of the dolomite series, and is a presumably very

Table 4. Chemical analyses of zincian dolomite

I-a

E..,

u
•...

c,..,
.E

eo

'03

~

CaCOl
ZnCOl
MgCOl
FeCOl
MnCOl
DuftiteMalachite
Sum

'"
",I::

53.52
11.88
26.11
0.03
0.05
7.58
0.33
99.50

I-b
51.58
15.11
33.21
0.04
0.06

I
I
100.00002339 }MgCOlo.~ FeCOl~~ MnCOl

0.76430.00070.0011

bO

~o

~\O

0:1

II-a

II-b

52.21
12.73
25.54
1.34

51.23

0.15
7.64
0.21
99.82

0.18

53.33
3.72
40.12
2.80
0.23

I
I

I
I

100.00100.00

15.62
31.33
1.64

i.ooooi.oooo0'" CaCOl•...••..
"'><: ZnCOl._

Sample III

Sample II

Sample I

00243'}~.....;

0.72590.02760.00311.001200OS57}~ 0.8939.....;0.0454
0.0038~dNote - Columns I-b and II-b: recalculated weight percent after
subtraction of duftite and malachite, and of 12.98 and10.44 percent CaCOl respectively (no excess CaCOl in
Sample III). See text.
The Mineralogical Record, May-June,1982rare Tsumeb secondary mineral, seems to be conclusively established. This conclusion is fully supported by the very good agreement between chemical, optical and physical data. As far as
chemical composition, indices of refraction and specific gravity areconcerned, and using the well-known Gladstone-Dale relationship,compatibility indices of -0.018, -0.015 and -0.011 can be found forminrecordite(averaged values) and magnesianminrecordite(analyses I and II) respectively. Such values are listed as "superior"by Mandarino (1979). It is significant that the best agreement isobserved for sample II of magnesian minrecordite: it gives fulljustification for the assumptions made in order to calculate its formula.
The possible existence of a pure compound CaZn(C03h with adolomite-like, ordered structure (and more generally the stability oftransition metal "dolomites") was recently discussed by Rosenberg
and Foit (1979). According to these authors, small cation size cannot be the only critical factor controlling the stability of these structures, which chiefly depends upon the distortion of R+206 octahedra, R+2 being a cation of a transition metal. Octahedral distortion apparently raises the free energy of formationof these
dolomite-like structures, until they become metastable phases,
when the sum of free energies for two binary disordered solid solutions is reached.
Many works on this subject (e.g. Goldsmith and Northrop, 1965)
suggest the following series in order of decreasing stability:
Mg » Mn : Zn : Fe) Co ) Ni » Cu
According to Rosenberg and Foit (1979), the stability limit for adolomite-like structure occurs in the vicinity of Zn in the above
series. These authors state that: "Zn-dolornite is probably not astable phase, although very extensive solid solution toward CaZn
(C03h is predicted." Actually, accepting the hypotheses assumed
by Rosenberg and Foit, it is possible to calculate, for Ca(Zn,Mg)(C03h a stability limit, which lies at a maximum Zn content (inatoms) between 85 and 90 percent of the small cations. We find, forpure minrecordite from Tsumeb, a value of 91. 7 percent (or a little
more, including Fe), which seems to agree with the provisions, taking into account the approximations
involved in Rosenberg andFoit's calculation.
Moreover, it is likely that minrecordite is not grown under ideal
conditions of chemical equilibrium. Analytical data seem to indicate that minrecordite chemical composition varies from one pointof growth to the next. It is possible that surface equilibria between
solutions and growing crystals may have played an important rolein the formation of this mineral (and of the associated zincian
dolomite). This was pointed out by Tsusue (1967) for rhodochrosite
and magnesian kutnohorite, and by other authors (e.g. Sims andBarton, 1(61) for different hydrothermal minerals.
Theparagenetic
position of minrecordite falls within the sequenceoutlined
by Keller (1977): dolomite - duftite - plancheite- dioptase I - calcite - dioptase II. Apart from the absence ofplancheite, the main difference between the above-mentioned
sequence and that observed on the minrecordite-bearing
specimen is
the presence of minrecordite instead of calcite in the position statedby Keller. However, the inspection of many dioptase druses from
Tsumeb leads us to consider the occurrence of a dolomitic phase (asthe intermediate between dioptase I and II) as not uncommon.
These dolomitic phases are most commonly represented by nearlypure dolomite or, less commonly, by zincian dolomite. The deposi, tion of minrecordite is probably due not only to an adequate concentration of Zn in the circulating solutions, but also to a quite uncommon scarcity of Mg in the latter, and perhaps (Keller, 1977) to aslightly higher environmental pH. The deposition of crystals ofcomposition not too different from the ideal CaZn(C03h must, inany case, be considered a rather uncommon event.
A careful examination of the many dioptase druses from Tsumeb
might result in the discovery of other minrecordite specimens. Their

The Mineralogical Record, May-June, 1982

identification must be achieved by accurate chemical, optical or
X-ray studies because of the close similarity, in outward appearance, to some dolomite (or, particularly, zincian dolomite) crystals.
With regard to the presence of zincian dolomite among the secondary minerals from Tsumeb, this compositionalvariety waspreviously described (or merely mentioned) for the locality by
Hurlbut (1957); Strunz, Sohnge and Geier (1958); Geier and Weber(1958); Geier (1974); and Pinch and Wilson (1977). In these studies,
the name "Zn-dolomite" (or "zinkdolomit") was used to mean acompositional variety, as stated, for example, by Geier (1974). On
the other hand, Rosenberg and Foit (1979) used "Zn-dolomite" as aname for the compound CaZn(C03h. Taking into account this ambiguity, and because of the introduction of the name minrecordite,it seems better to drop "zinkdolornit" and "Zn-dolomite," in favorof zincian dolomite, when the purpose is to designate a compositional variety.
All the zincian dolomites previously described for Tsumeb lie
below this compositional limit: their maximum Zn value is quoted
as 21.65 percent ZnC03(private communicationof Geier in
Strunz, 1970). Assuming that no other substitutents for Mg, in significant amounts, are contained in it, this would correspond to an
atomic ratio Zn:Mg not far from 1:2.
A zincian dolomite described by lasienska and Zabinski (1972)
seems to be much richer in Zn. This was found as a major mineralcomponent of an oxidized zinc ore from the Warynski mine, near
Bytom (Upper Silesia, Poland). These authors state that, in thissolid solution, the Zn:Mg atomic ratio "is approximately equal to oreven exceeds I." The results of microprobe analyses were: Ca =16-18 percent, Zn = 10-14 percent, Mg = 3-4 percent, Fe ( I percent. If the semiquantitative
evidence from these values is confirmed, then also these mixed crystals from Silesia might be classed
within the minrecordite range.

ACKNOWLEDGMENTS
The authors sincerely thank Richard C. Erd for reviewing themanuscript and offering many helpful suggestions. Our thanks also
to Giorgio Sala for assistance in the photographic work.
ADDENDUM
During 1980 and the first half of 1981, we examined vast
numbers of dioptase druses from Tsumeb in the hope of encountering another minrecordite specimen.
After the above manuscript was written, we were fortunate
enough to find, among a great many dolomite and some zincian
dolomite-bearing
dioptase druses, a small (18 x 26 mm) specimen
with a number of minrecordite crystals.
These crystals have the very same external appearance as described here for pure minrecordite crystals. A quantitative estimation of the major elements indicated, however, an atomic ratio Ca :Zn : Mg = 1.00: 0.65 : 0.25. Fe and Mn were not determined; theanalysis sums to 97.6, calculating the metals as carbonates. In spiteof its outward appearance, this mineral is therefore a magnesianminrecordite.
In this new magnesian minrecordite
specimen, some clear
rhombs are present, quite similar to the first-found magnesianminrecordite,and apparently formed after dioptase but before
minrecordite. These rhombs proved to be merely zincian dolomitewith an atomic ratio Ca : Zn : Mg = 1.00: 0.19 : 0.78 (Fe and Mn
were not sought).
This specimen was kindly submitted to our attention by Natale
Borghi, a skilled and esteemed mineral collector and dealer inRome. It was obtained about six years ago from Sid Pieters ofWindhoek, Namibia.
The new chemical data, though approximate,strengthen the
conclusion that compositional differences may exist among minrec135

ordite crystals grown at different locations within the Tsumeb oxidation zone, or even at the same point but at different times. Therefore, the chemistry of growing minrecordite appears very sensitive
to the composition of the circulating solutions.

REFERENCESGEIER, B. H. (1974) Mineralogische Studie der Blei-, Zink- undKupferlagerstatte
Tsumeb. Journal S. W.A. Wissenschajtliche
Gesellschaft, 28, 35-52.
__, and WEBER, K. (1958) Reinerit Zn3(As03h ein neues
Mineral der Tsumeb Mine Siidwestafrika. Neues Jahrbuch fur
Mineralogie, Monatshefte, 7/8, 160-167.

GOLDSMITH,
J. R., and GRAF, D. L. (1958) Relation between
lattice constants and composition of the Ca-Mg carbonates.
American Mineralogist, 43, 84-101.
__, and NORTHROP,
D. A. (1965) Sub solidus phase relations in the systems CaC03-MgC03-CoC03
and CaC03MgC03-NiC03.
Journal oj Geology, 73, 817-829.

HURLBUT, C. S. Jr. (1957) Zincian and plumb ian dolomite from
Tsumeb, South-West Africa. American Mineralogist, 42, 798803.
JASIENSKA,

S., and ZABINSKI,

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investigation of unusual zincian dolomite from the Warynski
mine (Upper Silesia). Mineralogia Polonica, 3, 67-70.
KELLER, P. (1977) Paragenesis. In: Tsumeb! The world's greatest
mineral locality. Mineralogical Record, 8, no. 3, 38-47.
MANDARINO,
J. A. (1979) The Gladstone-Dalerelationship.
Part. III: some general applications.
Canadian Mineralogist,
17,71-76.
PINCH, W. W., and WILSON, W. E. (1977) Minerals: a descriptive list. In: Tsumeb! The world's greatest mineral locality. Mineralogical Record, 8, no. 3, 17-37 (see also: "Errata" in: Tsumeb
Notes. Mineralogical Record, 9, no. 1,45).
ROSENBERG, P. E., and FOIT, F. F. (1979) The stability oftransition metals dolomites in carbonate systems: a discussion. Geochimica et Cosmochimica Acta, 43, 951-955.
SIMS, P. K., and BARTON, P. B. Jr. (1961) Some aspects ofgeochemistry of sphalerite, Central City district, Colorado.
Economic Geology, 56, 1211-1237.
STRUNZ, H. (1970) Mineralogische Tabellen (5 Aufl.).
mische VeriagsgeseIIschaft, Leipzig, p. 283.
__

Akade-, SOHNGE, G., and GEIER, B. H. (1958) Stottit, ein neues
Germanium-Mineral,und seine Paragenese in Tsumeb. Neues
Jarbuch fur Mineralogie, Monatshejte, 7/8, 85-96.
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The Mineralogical Record, May-June, 1982