604

SHORT COMMUNICATIONS(Na light) a 1"741, fl 1"746, y 1"755 (all •Ferrous iron wasdetermined by fusion of the mineral in sodium metafluoroborate,
following the procedure given by Groves (1951); water by a modified
Penfield method, the minera] sample being heated in a silica tube forhalf an hour by an oxy-coal gas burner, the temperature reached being
about 1300 ~ C. The number of metal atoms have been calculated on thebasis of 48(0,0H) to the unit cell: Si 7.807, A1 17.163, Fe" 0-706, Ti0-178, Mg 0.874, Fe" 2-515, Mn 0.015, Ca 0-064, OH 3-510; A I + F e "17.869 ; F e " + T i &c., 3.646. If Ti and Ca are grouped with Fe", Mg, andMn, the resultant formula agrees best with that proposed by Juurinen(1956), namely Fe4AllsSisO4,(OH)4.

Research School of Physical Sciences,5[. J. SNELLING.
Australian National University,Canberra, Australia.
BAEROW(G.) et al., 1912a. Explanation of Sheet 65. Mem. Geol. Surv. Scotland.
BARROW(G.), 1912b. Prec. Geol. Assoc., voh 23, p. 274.
GROVES(A. W.), 1951. Silicate Analysis. 2nd edn., London.
JIIVRI~N (A.), 1956. Ann. Acad. Scient. Fenn., ser. A, vol. 3, no. 47.

Serpierite .from the L a k e District.
SEaP~ERITE, a basic sulphate of copper, zinc, and calcium, was firstdescribed in 1881 from the Camareza section of the Laurium mines inGreece; in 1927 Sir Arthur RusselP described a second occurrence at
Ross Island, Killarney, Co. Kerry, in Ireland, this being the first andhitherto only known locality in the British Isles. One other locality, inKazakhstan, in the U.S.S.R., has since been recorded, but it is a raremineral.
We have recently found and confirmed the occurrence of serpierite at
two localities in the northern part of the Lake District. First, at Driggith
Mine, Caldbeek, where in some massive, intergrown chalcopyrite andblende, derived from the 30-fathom level, serpierite occurs in narrowveinlets or coating surfaces of joints ; it forms aggregates of tiny, paleblue, lath-like crystals, with a pearly lustre, and at first sight could beconfused with aurichalcite. Its identity was confirmed by powderphotographs which exactly match that of authenticated serpierite fromLaurium. On some of the specimens from Driggith mine the serpierite
is intimately associated with another pale-blue, pearly mineral, in
minute hexagonal plates, which gives an entirely different but welldefined powder-pattern, but has so far remained unidentified.

SHORT COMMUNICATIONS

605

The second occurrence is in a small copper vein near Potts Gill, whichhas produced an astonishing variety of secondary copper, lead, and zincminerals and which we hope to describe shortly. At this locality theserpierite forms tufts of minute, pale-blue needles and resembles theRoss Island and some of the Laurium material; it is associated withsmithsonite, malachite, aurichalcite, and other secondary copper
minerals.

Department of Mineralogy,
University of Oxford.
Department of Geology,
University of Leeds.

ARTI~Utr W. G. KINGSBUI~Y
J. tIAttTLEY

1 Min. Mag. 1927, vo]. 21, p. 386~-Manganese dioxide from Mysore, India.
DURINa an examination under the ore-microscope of manganese orefrom Mysore (My 4, Bidarematti, Kumsi area), I noticed a few clumps
of slightly fibrous and platy, greyish-white mineral associated withpyrolusite. An X-ray powder photograph of the mineral using Fe-K
radiation gave a different pattern from that of pyrolusite. The spacings
observed and tabulated below agree fairly well with the values of
McMurdie and Golovato 1 for ~-MnO~; 2 the intensities are estimated,and b indicates broad lines:
d,/~.
I

3-15
12-41
10b

2.15
9b

1-83
11.64
8b1-5321-34
4bA synthetic, electrolytically deposited y-Mn02 from Japan was furnishedfor m y study by the Winchester research laboratory, New Haven, Connecticut ; it gave a pattern in fair agreement with the above spacings.
Differential thermal curves were obtained for both the synthetic andthe naturally occurring mineral from Mysore; both show a significant
endothermic peak at 600 ~ C. and minor peaks at 250-300 ~ C. and 950 ~ C.
The steep peak exhibited at 600 ~ by the synthetic material is probably
due to its fineness and purity.
'y-Manganese dioxide' is unstable at high temp3ratures. X-ray
photogra16hs of the mineral taken after heating to 503 ~ C. showed apyrolusite pattern, hence the y-dioxide could be considered as poorly
crystallized pyrolusite, but the exact nature of it is still uncertain.
The oxide is of considerable industrial value. Recent research in