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Sodium-zippeite from Geevor mine, St. Just,Cornwall~ODIUM-ZIPPE1TE, Na4(UO2)6(SO4)3(OH)l 0.
4H20, is the most common member of thezippeite group which includes six naturally occurring hydrated basic uranyl sulphates, distinguished by the monovalent or divalent cations
they contain. Zippeite itself is the potassiumform, K4(UO2)6(SO4)3(OH) 10.4H20.
The name 'zippeite' was first applied by Haidinger (1845) to an earthy yellow uranyl sulphatefrom Joachimsthal, Czechoslovakia, which had
earlier been described by John (1821). However,the presence of potassium as an essential cation
was not recognised, nor were the other groupmembers described, until the comparatively
recent work of Frondel et al. (1976). The earlynomenclature and mineralogy of zippeite andrelated minerals were confused owing to difficulties in their study (Frondel, 1952; 1958; Frondel
et al., 1976). British records of 'zippeite' prior to1976 (e.g. Greg and Lettsom, 1858; Collins, 1871;
Dines, 1930; James, 1947; Robson, 1948) should
be regarded as references to unspecified minerals,
either of the zippeite group, or merely of zippeitelike appearance. The crystallography of the groupremains poorly characterised (Smith, 1984).
Zippeite and sodium-zippeite are the only
members with a monovalent cation and only
limited substitution between the K and Na
members occurs (Frondel et al., 1976).
In the course of several visits to Geevor mineduring the early part of 1991, zippeite-like minerals were collected from a number of undergroundlocations. Samples representing a range of habitsand colours from the various locations wereexamined by energy-dispersive X-ray analysis and
X-ray diffractometry. All specimens were confirmed to be sodium-zippeite and no othermembers of the zippeite group were identified.
The habits and mineral associations of thesodium-zippeite were rather variable and arediscussed by location below.
14 Level, No. 2 Branch. Pale lemon-yellow
sodium-zippeite from this location occurred on a
granitic matrix (largely quartz and orthoclase) in
the roof of a drive along the lode, generally
forming masses of broad, but extremely thin,translucent, interlocking leaves of indistinct

shape (Fig. l), but also as stouter laths andspindles. Associated minerals included gypsum,atacamite, chalcocite and brochantite. On somespecimens, johannite underlay sodium-zippeite,
and on one of these, antlerite was observed as apowdery blue-green deposit on the matrix.
16 Level, Hanging Wall Vein West. Heresodium-zippeite occurred as a cream-yellow
efflorescence composed of minute tabular crystals(similar to Fig. 2), following joints in alteredkillas. Spots of chalcopyrite occurred within thekillas. Gypsum was abundant and some of thesodium-zippeite was found intergrown with small
aggregates of atacamite crystals.
17 Level, Peeth Lode. An area along the drive
on Peeth lode, close to the intersection with
Whiskey Central lode, was particularly rich insecondary uranium minerals. The distribution ofspecies was zoned along the drive, extending overa distance of approximately 20 m. Schr6ckingeriteand andersonite occurred towards the westernend of the mineralised area (Elton and Hooper,1992). These species were generally not observedin close association with other uranium minerals,
although scattered blobs of sodium-zippeite wereseen on one or two specimens. Around the centreof the area, johannite occurred in close association with sodium-zippeite which was present in
two habits: small pale-yellow globular aggregatesof randomly orientated acicular crystals of indistinct shape, and as radiating groups of thicker,
darker laths. The matrix was typically quartz veinmaterial spotted with sulphide minerals (mainly
chalcopyrite), with gypsum as a common associate. Further east along the drive, sodium-zippeite
was found on the joint planes of unaltered granite
forming bright lemon-yellow mats and spherules,
composed of short indistinct spindles, widelyscattered over the surface of the granite. Johannite also occurred in this area, together with afinely crystallised, but unidentified, hydrated
sodium uranyl sulphate. H6wever, these species
werenotfrequentlyaccompaniedbysodium-zippeite.
17 Level, Levant North Lode East (No. 2Branch, adjacent to 17W3 cross-cut). This location
produced sodium-zippeite in the widest range ofSHORT COMMUNICATIONS

353

FIG. 1. (Top left). Intergrown mass of extremely thin and indistinct leaves of sodium-zippeite. 14 level, no. 2 branch,Geevor mine. Fro. 2 (Top right). Tabular crystals of sodium-zippeite forming powdery deposits. 17 level North lode,Geevor mine. Fro. 3 (Bottom left). Divergent group of tapering laths and parallel aggregates of poorly terminatedlaths of sodium-zippeite. 17 level North lode, Geevor mine. Fro. 4 (Bottom right). Intergrowth of tabular crystals ofsodium-zippeite. 17 level North lode, Geevor mine.
habits and colours. Specimens were collectedfrom a small area of partially altered and collapsed wallrock, traversed by a narrow vein
carrying various sulphide minerals, notably chalcocite, but also chalcopyrite, and more rarely,arsenopyrite. Most of the sodium-zippeite wasfound on a matrix of quartz and pinky-red
orthoclase and occurred as intergrowths of finetranslucent, petal-shaped laths to around 1 mm,
forming booklets and 'desert rose' aggregates. It
was found also as sprays of very fine narrow laths
and spindles (Fig. 3) and as stacks of stout plates(Fig. 4). On a few specimens, sodium-zippeite
also occurred in an opaque earthy form composedof microcrystalline tablets (Fig. 2). Sodiumzippeite frequently encrusted atacamite, butmany specimens also showed small crystals of
atacamite scattered over the sodium-zippeite. In
addition to the minerals noted above, gypsum,chalcanthite, brochantite, antlerite, and rarely,metazeunerite and scorodite, were also recorded
from the same area (approximately 3 m inextent).

Frondel et al. (1976) contrasted the 'yellow'
colour of sodiurn-zippeite with the 'goldenyellow' colour of zippeite. The colour of theGeevor sodium-zippeite varied from lemonyellow to orange-yellow. The colour of powderedmaterial was more consistent, and some of theapparent colour variation of the crystallisedmaterial appears to be due to variations in matrix
colour and transparency of the crystals. Theorange-yellow colour of certain crystals, notablyvermicular aggregates of thin tabular crystals
from North Lode, can be attributed to a lightstaining of iron oxide.
The areas described above are all on levels
which extend beneath the seabed. Percolatingwater in the mine at these levels is very saline,
creating an abundance of sodium ions. This may
explain the apparent absence of zippeite proper.
Frondel etal. (1976) observed that zippeite
placed in a concentrated solution of NaC1 slowly
recrystallises to sodium-zippeite, the reaction
being irreversible. The copper chlorides, atacamite, and less commonly, paratacamite were354

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observed in close association with the sodiumzippeite on several specimens and are probably
derived from the action of salt water on primarysulphides. Botallackite was also recorded within
the mine, but not in association withsodium-zippeite.
Gypsum, johannite and andersonite have beenfound associated with sodium-zippeite at otherlocalities (Frondel etal., 1976). Synthesis andstability studies show that andersonite is only
stable when the activity of Na is very high and thatof Ca and Mg very low (Alwan and Williams,1983). It is likely that such conditions within
Geevor mine would favour the formation ofsodium-zippeite rather than zippeite.
Samples of sodium-zippeite have been lodged
with The Natural History Museum, London.
Acknowledgements. The authors wish to thank Dr.
R. F. Symes for reviewing an earlier draft of this paperand for access to specimens in the NHM collections andDr. G. Ryback for assistance with infra-red identifications. The authors are also grateful to ECC International for the use of analytical instrumentation.
References

Alwan, A. K. and Williams, P. A. (1980) Mineral.
Mag., 43,665-7.

Collins, J. H. (1871) A Handbook to the Mineralogy ofCornwall and Devon, Truro.
Dines, H. G. (1930) Mining Mag. April 1930.
Elton, N. J. and Hooper, J. J. (1992) Mineral. Mag., 56,124-5.
Frondel, C. (1952) Amer. Mineral., 37, 950-9.
- - ( 1 9 5 8 ) U.S. Geol. Surv. Bull., 1064, 400 pp.
- - I t o , J., Honea, R. M., and Weeks, A. M. (1976)
Can. Mineral., 14, 429-36.
Greg, R. P. and Lettsom, W. G. (1858) Mineralogy ofGreat Britain and Ireland, Van der Voorst, London(republished 1977, Lapidary Publications, Broadstairs, Kent).
Haidinger, W. (1845) Handbuch der bestimmenden
Mineralogie, Vienna. [Not seen: quoted in Frondel(1958)]
James, C. C. (1947) Trans. Roy. Geol. Soc. Cornwall,17, 256-68.
John, J. F. (1821) Chem. Untersuch., 5, 254; Chem.
Phys., 32,248. [Not seen: quoted in Frondel (1958)]
Robson, J. (1948) Trans. Roy. Geol. Soc. Cornwall, 18,455.
Smith, D. K., Jr. (1984) Uranium Mineralogy. In
Uranium Geochemistry, Mineralogy, Geology,
Exploration and Resources (De Vivo, B. et al., eds.),
Institution of Mining and Metallurgy.
[Manuscript received 22 June 1992;
revised 18 September 1992]
9 Copyright the Mineralogical Society

KEYWORDS: sodium-zippeite, zippeite, Geevor mine, Cornwall.

Tregears, Little Treviscoe, St Austell, Cornwall PL26 7QL

N. J. ELTON

48 St. Julitta, Luxulyan, Bodmin, Cornwall PL30 5ED

J. J. HOOPER

M I N E R A L O G I C A L M A G A Z I N E , JUNE 1993, VOL 57, PP. 354-357

Cordierite-K-feldspar-quartz-orthopyroxene
symplectite from southern Algeria: new evidence
for osumilite in high-grade metamorphic rocks
IN recent years, osumilite, (K,Na)(Mg,Fe,Mn)2(A1,Mg,Fe3+)3(Si,A1)12030,
has
beenreported from a number of high-temperature
granulite facies terranes (for example, Berg andWheeler, 1976; Ellis etal., 1980; Grew, 1982a;
Arima and Gower, 1991). In addition, there are a
few localities where osumilite is thought to havebeen stable as evidenced by its characteristic

breakdown products (Ellis etal., 1980; Grew,1982b; Nicollet, 1988). In this paper, a new
occurrence of this type is reported in granulitefacies rocks from the In Ouzzal block, southern
Algeria. The stability of the primary mineral
association involving osumilite is then discussedin the light of preliminary experimental results in
the KFMAS system.