128

Mineralogy of the Silvermines district, County
Tipperary, Eire.
(With Plates IV to VI.)B y H. N. RHODEN, Ph.D., D.I.C., A.R.S.M.
Redhill, Surrey.
[Communicated by Dr. A. P. Millman, taken as read 2 April 1959.]

Summary. The paragenesis of a suite of hydrothermal minerals (sulphides,
baryte, rhombohedral carbonates, quartz, sericite, and chlorite) at four mines inthis district is discussed. Of particular interest are the conversion of pyrrhotine tomarcasite, which is shown to take place by loss of iron, the replacement of blendeby chlorite, and the possible formation of primary goethite. The occurrence of
gudmundite is recorded for the first time in the British Isles.
' U S T over fifty years ago, Russell (1907) published in this journal'Notes on the Mines and Minerals of the Silvermines District,County Tipperary'. A recent survey of various eighteenth- and nineteenth-century workings and one modern productive lead mine nearSilvermines, coupled with microscopic examination of the ores, hasrevealed the presence of additional minerals and some unusual texturalfeatures.
A fuller description of the mines, local geology, and economic
mineralization has been published elsewhere (Rhoden, 1958a, 1958b).
Briefly, the ore deposits occur in Devonian and Carboniferous rocks
bordering the Silvermines Fault, which is a complex system of maior
and t r i b u t a r y fractures t h a t can be traced for over 25 miles acrossnorthern Tipperary and southern Clare.

J

Shallee and Gortnadyne mines.
At Shallee mine, ramifying veinlets of galena, baryte, and otherminerals, listed in orde~ of deposition in table I, are concentrated beneathgently dipping shale horizons in strongly fractured Devonian sandstones.
A t Gortnadyne mine the copper lode consists mainly of brecciatedDevonian sandstone, re-cemented b y quartz, sulphides, baryte, andcarbonates.
Although dislocation of the beds preceded the onset of mineralization,
structural dilation of the fractures continued throughout the sulphide
phases, and finally ceased during the deposition of baryte, which filledTHE MINERALOGY OF THE SILVERMINES DISTRICT129

TABLE I. Epigenetic minerals at Shallee and Gortnadyne mines.

Paragenesis.
Primary minerals.
Early.
Sulphidation of wall-rocks(Pyrrhotine)
Arsenopyrite(Chalybite)*

La~.

QuartzPyriteBlende (~Cu)
Chalcopyrite
Tetrahedrite
Gudmundite*
Marcasite
Bournonite
Boulangerite*~
Goethite*
Sericite
Chlorite
GalenaBlende (pure)Ankerite
BaryteSecondary minerals.
Chalcocite
Malachite
I-Iemimorphite$
Covelline
AzuriteLinarite:~* Microscopic identification.
t Shallee only.
:~ Gortnadyne only.

Goethitethe remaining space in the veins and breccias. During mineralization,
the red and buff sandstones and shales were bleached to light grey andolive-green colours respectively, with redeposition of sedimentary hematite and goethite as pyrite; at the same time, ilmenite grains were
replaced by clusters of rutile crystals set in translucent leucoxene andquartz.
The first epigenetie mineral of which traces still remain was pyrrhotine.
P l a t y crystals, up to 1 inch square, grew parallel to the sandstone wallrocks, giving the veins a streaky appearance. After slight fracturing, thepyrrhotine was often surrounded b y euhedral crystals of arsenopyrite,and of a rhombohedral carbonate t h a t was afterwards converted toankerite and goethite (see p. I33), before being finallyset in a matrix ofquartz and later sulphides. During the subsequent deposition of copper,
antimony, zinc, and lead minerals, all the pyrrhotine changed to marcasite and pyrite (see p. 131).
Of the principal minerals, pyrite was deposited earliest. Small pyrito-

130

H.

l~I. RHODEN

ON

hedra line the veinlets at Shallee mine, and are scattered throughout thesandstone and shale wall-rocks, having formed at the expense of sedimentary iron oxides. A few thin beds of dolomitic and sandy shale,
however, contain abundant needles of arsenopyrite, to the exclusion of
pyrite, indicating that arsenic may have been an original constituent of
the rock (Goldschmidt and Peters, 1934).
Two forms of blende occur: one is dark brown, iron-rich, and often
contains tiny inclusions of exsolved chalcopyrite ; the other type is lightyellow and free from inclusions. Deposition of the dark variety, which
is more common at Gortnadyne than at Shallee, overlapped the formation of pyrite, producing alternate colloform banding. The purer blende
was the last sulphide to crystallize, and is often associated with veinlets
of ankerite. Chaleopyrite, followed closely and partly replaced by tetrahedrite, succeeded pyrite at both mines, but attained economic grade
only at Gortnadyne.
The most abundant sulphide in the veins at Shallee mine, and probably
also in the breccia at Gortnadyne, is galena; but if the 'ore' is assumed
to include the inter-vein sandstone, galena may be exceeded by pyrite.
Although galena slightly replaced all the earlier minerals, most of it was
deposited ill open fissures; but in places where the vein-walls had not been
lined by pyrite or chalcopyrite, galena also replaced quartz and claymica minerals to give the marginal sandstone a distinct blue-greycoloration. Galena at Shallee mine contains 44 to 53 oz. of silver per
tong ton of lead metal (production data for 1949 to 1958), and at
Gortnadyne, 20 to 25 oz. per long ton (Wynne, 1861).
A remarkable feature of the galena at Shallee mine is the multitudeof inclusions of bournonite, boulangerite, and tetrahedrite. Some tetrahedrite grains are plainly relics left during the replacement of surrounding chaleopyrite; part of the bournonite may be a reaction 'front'
between partly replaced copper minerals and galena ; but most inclusions
are remote from such replacement contacts, and the microscopic texture
indicates that they have exsolved from the galena during cooling.
Boulangerite occurs as a ' rash' of tiny untwinned laths up to 40/z long,oriented along crystallographic planes within the galena. Bournonite
inclusions, showing excellent parquet-like twinning, are larger and morerounded in shape, and tend to segregate at grain boundaries, leaving
peripheral areas of the galena free from inclusions. Tetrahedrite is lesscomnmn away from contacts with copper minerals, but occurs in thegalena like bournonite. Inclusions of different minerals are never intermingled, but may occur in neighbouring grains of galena. AlthoughTHE M I N E R A L O G Y

O~' T H E SILVEII, M I N E S

DISTttICT

131

direct evidence is lacking, exsolution probably commenced with tetrahedrite, continued with bournonite, and ended with boulangerite ; thetype of inclusion produced in each grain of gale~la would depend on theconcentration of copper and antimony, and on the original temperatureof deposition. In direct contrast, galena at Gortnadyne mine rarely
contains any exsolved minerals.
The growth of fibrous mats of chlorite and sericite in open veins at thisstage of mineralization is described below (p. 134). Deposition of creamycoloured anl~erite (~o 1"712 to 1.720), containing a trace of manganese,
probably started shortly after the pyritic stage, but reached a modest
peak as sulphide mineralization ended with the crystallization of lightyellow blende (see table I). The carbonate at Gortnadyne is contaminated by the presence of dolomite in parts of the breccia. Anyremaining space in the veins or breccias was filled by pure white baryte,
the last primary mineral deposited. The usual range of secondary
minerals, listed in table I, developed during erosion.
Conversion of pyrrhotine to marcasite. The alteration of pyrrhotine tomarcasite and pyrite is not a rare phenomenon in moderate to lowtemperature sulphide deposits, 1 having been first reported over fifty
years ago (referred to by Allen, Crenshaw, Johnston, and Larsen, ]912).
Some writers (summarized by Edwards, 1954) consider that the change
occurred during the closing stages of mineralization, while others (Foslie,1950) regard it as a supergene process. Although similar conversions ofpyrrhotine to marcasite have been observed in ores from Abbeytown,
Co. Sligo, Eire, and from Stari Trg, Trep6a, Yugoslavia, the uniquesuite 2 of minerals from the Silvermines district establishes the exact
point during the primary mineralization at which the alteration occurred.
As the first epigenetic mineral, pyrrhotine crystallized only in the'strongest' veins at Shallee mine, and in the breccia at Gortnadyne.
Single platy crystals with sharp edges, illustrated in pl. V, fig. 3, grewparallel to the vein wall, giving an appearance of 'flow texture' to theveins ; pyrrhotine never occurs in the granular or rosette form commonly
found at other deposits, 1 including Abbeytown and Trep6a. After being
lightly fractured, the pyrrhotine plates were partly covered by arsenopyrite (shown in p1. IV, fig. 1) or carbonate (possibly chalybite, see
p. ]33) crystals, before being finally set in quartz and later sulphides.
1 Described by O'Malley and McGhie, 1939; Stillwell and Edwards, 1943, 1945,
1946 ; Stillwell, 1944 ; Carter, 1948.
2 Type samples from Shallee and Gortnadyne mines are included in the referencecollections of Economic Mineralogy at the Imperial College of Science and Technology, London.

132

H.N.

RHODEN

ON

Pyrrhotine remained stable throughout the pyritic stage of mineralization, but changed entirely to marcasite and pyrite during the subsequent deposition of copper, antimony, lead, and zinc minerals. Despite
the simultaneous crystallization of iron-rich minerals, such as blende,chalcopyrite, and tetrahedrite, nearby and even within the pseudomorph, the pyrrhotine altered to disulphide by expelling roughly half
its original iron content, and without consuming additional sulphur(see below). As the conversion progressed, tiny shrinkage cracks opened
parallel to the basal parting of the pyrrhotine crystals, which otherwise
retained their shape. The reduction in volume from pyrrhotine todisulphide can be measured microscopically, and is remarkably constant
at 32 to 38 %.
Theoretically, the conversion of pyrrhotine to marcasite can take placein three ways (for convenience pyrrhotine is assumed to be FeS (troilite)) :constant volume, in which sulphur must be added to the system and ironremoved in the proportion expressed in the equation gFeSq-2S =3FeS~§
constant iron, in which sulphur is added (FeS+S = FeS2),
and the resulting marcasite occupies over 33 % more space than theoriginal pyrrhotine; and constant sulphur, in which almost half the ironis expelled (2FeS = FeSa§
leaving marcasite or pyrite to occupy
only 66'8 To or 65"2 To of the pseudomorph respectively. Althoughnatural pyrrhotine, which has a defect structure (Hfigg and Sucksdorff,
1933), varies in composition between F%+71S and F%.sgaS with consequent change in density, its original composition should not change theratio of atomic sulphur to molecular volume, nor affect the theoreticalshrinkage to marcasite or pyrite in a constant sulphur system.
By comparing the theoretical reduction in volume by 33"2 % for marc~site or 34~.8 % for pyrite with the measured 32 to 38 %, there can be
no doubt that the pyrrhotine at Shallee and Gortnadyne mines changed
to disulphide solely by the loss of iron. The same applies to the conversion of granular pyrrhotine at Abbeytown mine and Trep6a, and to thetypical 'bird's eye' textures observed ill other ore deposits.
As the pyrrhotine decomposed, the shrinkage cracks were filled by themineral being deposited in the vicinity. Most cracks contain chaleopyrite, tetrahedrite, iron-rich blende, galena, or quartz (see p]. IV,
figs. 1 and 2), any single crack usually being filled with more than one
mineral; less commonly, bournonite, boulangerite, gudmundite, a rhombohedral carbonate, and even later minerals, like iron-free blende andbaryte, may be included. Although most of the pyrrhotine changed tomarcasite, some idiomorphic pyrite developed near the edges of the

THE

MINERALOGY

OF

THE

SILVERMINESDISTRICT

133

pseudomorphs, breaking the continuity of the tiny shrinkage cracks(see pl. IV, fig. 1). The marcasite occurs as minute lath-shaped
crystals, oriented at right angles to the cracks and often separated
from each other by ahnost sub-nficroscopic partings containing otherminerals.
Gudmundite. Liberation of iron from the decomposing pyrrhotine
produced some unusual results in the narrow shrinkage cracks and along
the edges of the pseudomorphs. During an influx of tetrahedrite, amomentary excess of iron over copper would cause the deposition of
gudmundite (FeSbS), and the remarkable angular texture illustrated inpl. IV, fig. 2; the tetrahedrite crystals shown in pl. V, fig. 4, were partly
replaced by chalcopyrite, then covered by a thin, even layer of gudmundite, before remaining space in the centre of the crack was filled byquartz. Rarely, intergrowths of gudmundite and tetrahedrite occur
separately from the pyrrhotine pseudomorphs.
Although the properties of gudmundite closely resemble those ofarsenopyrite (Buerger, 1939), it can be readily identified in polishedsections by its strong rose-coloured pleochroism. Ridland (1941) reported a Talmage hardness of F for gudmundite, similar to arsenopyrite;
but most observers, including the writer, prefer a rating of D, closer totetrahedrite. The apparent rarity of gudmundite may be due solely tothe failure of many geologists to distinguish it from arsenopyrite.
Gudmundite, which is usually found in hypothermal deposits like thecomplex sulphide masses at Boliden (summarized by Sampson, 1941),
or the gold-stibnite veins of Southern Rhodesia (Morgan, 1957), has notbeen previously reported from the British Isles, and may occur in other
leptothermal deposits similar to those at Silvermines.
Replacement of carbonate mineral. The crystallization of a rhombohedral carbonate around pyrrhotine and on vein-walls before the deposition of pyrite was mentioned above (p. 129). Despite their characteristic
outline, the rhombs are invariably filled with a granular aggregate ofankerite and goethite, which vary widely in relative proportion. Interlocking grains of ankerite are rarely in definite orientation either to one
another or to the pseudomorph margins. In many pseudomorphs, likethat illustrated in pl. V, fig. 5, galena appears to vein and partly toreplace the aggregate along grain boundaries, or along the ankerite
cleavage. In most samples, the galena seems to be related to the existing aggregate rather than to any 'ghost' structure of an original single
carbonate crystal.
Theoretically, three interpretations of the texture are possible. Galena

13~

H.N.

RHODENON

may have veined and partly replaced either the original carbonate, theremainder of which changed to ankerite and goethite during supergene
alteration; or an aggregate of ankerite or chalybite, only the goethite
being formed later; or the present aggregate of ankerite and goethite,
this being a primary replacement of an original ehalybite crystal.
The third hypothesis accounts for the texture best, for goethite isalways present in the pseudomorphs, while surrounding sulphides show
no sign of supergene alteration. If the original carbonate was ehalybitethat had crystallized shortly after pyrrhotine, but before the complete
sulphidation of iron oxides in the surrounding sandstones, it may havebecome unstable during the later phases of mineralization, when true
ankerites were being deposited; as the chalybite changed to ankerite,some of the excess iron would remain in the pseudomorph as primarygoethite. In a low-temperature deposit, like that at Shallee mine, such
residual goethite might survive through the final stages of galena baryte
mineralization, for the decomposition temperature of goethite is about
150~ C. in neutral or weakly alkaline hydrothermal solutions (Smith andKidd, 1949). The formation of crystalline goethite in similar ores wasreported by Edwards (1955).
Redeposition of pyrite. Crystallization of pyrite and blende overlapped
at Gortnadyne mine, producing alternate colloform banding and mutual
replacement. The dark brown iron-rich blende illustrated in pl. V, fig. 6,
was lightly brecciated, then partly replaced by pyrite; subsequently,
both minerals were replaced by galena. But the texture shown in thisplate is unusual, for pyrite is moulded round typical galena crystals, andforms long, thin, broken veinlets along the cubic cleavage. This moulded
form of pyrite is usually devoid of relics of blende.
The best explanation is that as galena replaced both minerals, someof the pyritic material remained almost in situ, and was redepositedaround the growing crystals of galena, or along the cleavage ; slight pressure would break these narrow veinlets shortly after formation. Zinc,
however, would be removed from the site of replacement.
Chlorite and sericite in veins. Although extensive zones of alteration
are not discernible in the wall-rocks at Shallee mine, the sericitie
groundmass of sandstones and shales is often replaced by chlorite nearsome of the 'stronger' veins. During the later phases of mineralization(see table I), platy mats of chlorite and sericite lined the edges of freshly
opened fissures, which were subsequently filled with galena, ankerite, orbaryte. The feathery plates of sericite illustrated in pl. VI, fig. 9, curveand branch within galena without regard to the cubic cleavage; similarly,

THE MINERALOGYOF THE SILVERMINESDISTRICT

135

in other samples, chlorite plates finger into baryte crystals without
disturbing their optical continuity or utilizing their excellent cleavage.
In each instance, the microscopic texture indicates crystallization ofgalena and bary~e around the chlorite or sericite plates, rather thandevelopment of the latter in fractures in, or replacing, the galena andbaryte. Sometimes, rows of these plates lining a vein-wall are bent thesame way, suggesting the flow direction of the solution depositing theencasing mineral. Growth of chlorite and sericite in veins, probably
from material derived mainly from the wall-rocks, must be regarded asa distinct phase of mineralization, occurring just before the main deposition of galena and baryte.
Replacement of blende by chlorite. An unusual replacement phenomenon occurs at Shallee mine, in which isolated crystals of dark brown
blende containing exsolved inclusions of chaleopyrite are marginallyreplaced by bright green chlorite. The original outline of a euhedral
blende crystal, the margin of chlorite, and the unreplaced core, areillustrated in pl. VI, figs. 7 and 8. Irregular masses of light yellow blende,
shown in pl. VI, fig. 8, have replaced clay-mica minerals in the rockgroundmass surrounding the pseudomorph. Since the quantity of thelight yellow form is comparable with the amount of replaced copperrich blende, the inescapable conclusion is that blende replaced by chlorite
was immediately redeposited nearby purged of its inclusions. Much of
the uncommon, pure blende found at Shallee may have been derived
from an earlier copper-rich variety (see paragenesis in table I).
According to Hey's (1954) optical data, both chlorites (m = 1.64,
e--w = --0-004) mentioned above can be classed as brunsvigite.

Knockanroe and Ballygown South ~dnes.
Along the northern side of the Silvermines fault at Knockanroe andBallygown South mines, fractured dolomite near the base of the Carboniferous Limestone series contains disseminated pyrite, marcasite, blende,
galena, and baryte. During prolonged pre-glacial erosion of the orezones, sulphides were oxidized and the products, with baryte and silica,
became progressively concentrated with the removal of the host-rock.
Less soluble minerals, such as anglesite, cerussite, unaltered galena, andbaryte, accumulated on the surface with gossan. More soluble material,
like zinc and some iron, migrated downwards in sulphate solution to
replace fresh dolomite, forming smithsonite and chalybite respectively;
these, in turn, changed to hemimorphite and goethite as the level ofoxidation gradually deepened. The high-grade residual lead-silver

136

H.N. RHODEN ON

deposit, which gave rise to the n a m e ' Silvermines', was exhausted during
the seventeenth and eighteenth centuries; below it, the enriched zinciron ore=zone still remains, known as the 'Calamine Bed'. Primaryminerals identified at these mines are listed in order of deposition intable II, and secondary minerals in order of depth zones in table I I I .
TABLEII. Primary minerals at Knockanroe and Ballygown South mines.
Paragenesis.
Primary minerals.
Early.
Lat~.
PyriteMarcasite
Arsenopyrite
Blende(ex. pyrrhotine)*
GalenaBaryteDolomite(recrystallized)* Pyrrhotine exsolved from the earliest variety of blende, during cooling.
The first epigenetic minerals in the dolomite, or in the sandstone faultbreccia known as t h e ' Sulphur Lode', were pyrite and marcasite. Spherulites, up to 2 inches in diameter and composed mainly of radiating pyrite
crystals, often contain wedges or segments of marcasite; the relic texture
illustrated in pl. VI, fig. 10, indicates that clumps of marcasite crystals
in the centres of spherulites may subsequently change to pyrite. Slightvariations in pH caused by the dissolution of dolomite, rather than smallchanges in temperature, pressure, or concentration, would determine themineral formed at the point of precipitation at each moment (Allen,
Crenshaw, Johnston, and Larsen, 1912). As Tart (1927) suggested, marcasite would crystallize during an influx of slightly acid solutions, butpyrite would be deposited as the quantity of dissolved lime increased
and the temperature of the solutions decreased.
TABLEIII. Secondary minerals at Knockanroe and Ballygown South mines.
Depth zones.
Secondary minerals.
Goethite
Cerussite
Anglesite
Heminmrphite
Smithsonite
Chalybite

S-urface.

Shallow.

Deep'.

As in similar rocks at Shallee, abundant needles of arsenopyrite

TIIE

I~IINERALOGY

OF

THE

SILVERMINESDISTRICT

137

developed in certain thin shaly beds within the dolomite, to the exclusion of pyrite or marcasite.
Deposition of blende overlapped that of pyrite and marcasite, causing
alternate colloform banding round spherulites. The earliest blende wasa dark brown variety, containing up to 4 % Fe, from which pyrrhotine
subsequently exsolved; thereafter the blende became progressively purer,
until clear, light yellow crystals were formed at the end of mineralization.
The exsolution of pyrrhotine from blende at Knockanroe and Ballygown
South mines, rather than chalcopyrite as at all other deposits in theSilvermines district, is noteworthy; it indica~s that the total absence ofcopper minerals in the present superficial workings will probably continue in depth.
Deposition of galena started shortly after the earliest blende, butfinished just before the final and purest variety of the latter. The highsilver content of the lead ores made the locality famous in olden days;
the figure of 80 oz. of silver per lo~lg ton of smelted lead quoted by R u t t y(1772) and Wynne (1861) referred mainly to the oxidized ores, but
Apjohn (1860) confirmed the same quantity in fresh galena. The last
truly epigenetie mineral was baryte.
The hydrothermal minerals are closely associated with irregular veinlets of a light pink dolomite (~o 1"69) containing traces of iron and manganese, which has the same composition as the dark blue-grey host-rock.
Redeposition of dolomite started during the later phases of sulphidemineralization, and continued afterwards until most fissure and solution
cavities were sealed. At the western end of Knockanroe mine mostveinlets were filled with baryte, which effectively restricted the recrystallization of dolomite.
The secondary ores at these mines resemble 'calamine' deposits elsewhere. In the residual lead-silver zone, eerussite and anglesite replacegalena, often leaving a core of sulphide protected from oxidation. In
the deeper 'calamine' zone, clear crystals of hemimorphite (first discovered by Capt. King (Wynne, 1860), and identified by Apjohn (1860))
occur in an ochreous mass of goethite, ehalybite, smithsonite, unalteredprimary minerals, and brown-stained dolomite.

References.
ALL~ (E. T.), Cn~s~Aw (J. L.), JO~STO~ (J.), and LA~SE~(E. S.), 1912, Amer.
Journ. Sci., ser. iv, vol. 33, p. 169.
APJOHN(A.), 1860. Journ. Geol. Soc. Dublin, vol. 8, lo. 157.
B v ~ G ~ (M. J.), 1939. Zeits. Krist., vol. 101, p. 290 [M.A. 7-387].
CARTER(S. R.), 1948. 18th Int. Geol. Cong., London, pt. VII (1950), p. 195.

138~. iN~. RHODEN ON

EDWA~I)S (A. B.), 1954. Textures of the ore minerals and their significance, 2nd edn.
Australasian Inst. Min. Met., Melbourne.
1955. Proc. Australasian Inst. Min. Met., new ser., no. 175, p. 55.
FosmE (S.), 1950. Norsk. Geol. Tidsskr., vol. 28, p. 144 [M.A. 11-505].
GOLDSCHMIDT (V. M.) and PETERS (C.), 1934. Nachr. Gesel]. Wiss. GSttingen,vol. 1, p. 11.
I-IXco (O.) and SUCKSDORFF (I.), 1933. Zeits. Physikal. Chem., Abt. B, vol. 22,
p. 444 [M.A. 5-466].
HEY (M. H.), 1954. Min. Mag., vol. 30, p. 277.
MORGA~ (D. A. 0.), 1957. The Geology of the Sebakwe group of mines, Que Que,
Southern Rhodesia, with special reference to the gold ore. Ph.D. thesis,
University of London.
O'MALLEY (G. B.), and McGmE (R. R.), 1939. Proc. Australasian Inst. Min. Met.,
new ser., no. 116, p. 459.
RHODElV (H. N.), 1958a. The Geology and Mineralisation of the Silvermines Area,
County Tipperary, Eire. Ph.D. thesis, University of London.
-1958b. Trans. Inst. Min. Met., vol. 68, p. 67.
I~IDLAND(G. C.), 1941. Econ. Geol., vol. 36, p. 45 [M.A. 8-247].
RUSSELL (A.), 1907. Min. Mag., vol. 14, p. 350.
RUTTY (J.), 1772. An essay towards a Natural History of the County of Dublin.
2 vols., Dublin.
SAMPSO~ (E.), 1941. Econ. Geol., vol. 36, p. 175 [M.A. 8-275].
SMIT~ (F. G.) and KInD (D. J.), 1949. Amer. Min., vol. 34, p. 403 [M.A. 11 90].
STILL~rELL (F. L.), 1944. Proc. Australasian Inst. Mill. Met., new set., no. 135, p. 1,
and EDWARDS (A. ~B.), 1943. Ibid., nos. 131-132, p. 173.
- - - 1945. Ibid., no. 139, p. 149.
1946. Ibid., no. 141, p. 31.
TARR (W. A.), ]927. Amer. Min., vol. 12, p. 417 [M.A. 3-453].
WY~NE (A. B.), 1860. Journ. Geol. Soc. Dublin, vol. 8, p. 244.
-1861. Mem. Geol. Surv. Ireland, sheet 134.

-

-

-

-

-

-

-

-

-

EXPLANATION OF PLATES IV TO VI.

PL~-TE IV.
FIG. 1. Edge view of pyrrhotine pseudomorph, composed chieflyof marcasite, andsurrounded by euhedral arsenopyrite crystals, quartz, chalcopyrite, and tetrahedrite. In the pseudomorph, shrinkage cracks contain quartz (black), blende(dark grey), tetrahedrite (medium grey), chalcopyrite (light grey without relief),
and galena (light grey with strong relief) ; areas of plain relief near margins are
pyrite, which break the continuity of the cracks. Shallee mine, 320-ft. level,
9.6 W. stope; polished section • 170.
l~ia. 2. Pyrrhotine pseudomorph containing marcasite (light grey) ~nd quartz(black spots), with tetrahedrite (dark grey) in the shrinkage cracks. Angularlines are gudmundite, which covered the tetrahedrite crystals during
momentary pause in growth. Gortnadyne mine, breccia; polished section
x 930.

PLATE V.
FIG. 3. Side view of platy pyrrhotine crystals, showing sharp edges, surrounded byquartz (dark grey) and later sulphides (light grey shades). Pseudomorph filled

MIN. MAG., VOL. XXXII

H. N. RIIODEN: MINERALOGY OF THE SILVERMINES ])ISTRICT

Plate IV~[IN. MAG., VOL. X X X I []-~. ~k~.]:~HODEN: MINERALOGYOF THE SILVERMINES DISTRICT

Plate V[I~. MAG., VoL XXXII

i~!~ii~i~i~i!!~!~!!~%~;~i2::12:,. ,:~'::

Plate VI?~ :~ 9 9 9149149: 9149 :',: 9149149

9149149149149149149149149149.~'. >H. I~. I:~HODEN: MINERALOGYa

9149149 ~ .

v

9

9

; 9149149149

OF THE SILVERMINES:. 9149149149149149149

DISTRICT

THE MINERALOGY OF THE SILVERMINES DISTRICT

139

with marcasite, with other sulphides in shrinkage cracks parallel to basal
parting of original pyrrhotine. Shallee mine, 320-ft. level, 9"6 W. stope;polished section, • 41.
Fro. 4. Shrinkage cracks within pyrrhotine pseudomorph. Triangular-ended tetrahedrite crystals, which grew out from the marcasite edges, were partly replacedby chalcopyrite, then covered by a thin layer of gudmundite ; remaining spacein the crack was filled by quartz. Gortnadyne mine, breccia ; polished section,• 1230.
FrG. 5. Pseudomorphs of early carbonate (chalybite ?) crystals, filled with ankerite(darker grey shades) and goethite (lighter grey). Galena (white) embayed
and veined the pseudomorph, partly replacing both minerals. Shallee mine,
320-ft. level; polished section, • 148.
Fro. 6. Brecciated iron-rich blende (dark grey), partly replaced by pyrite (white) ;both minerals were subsequently replaced by galena {light grey, deep relief).
Some of the pyrite was redeposited around the developing crystals of galena,
or in long, thin, broken vein]ets along the cubic cleavage. Gortnadyne mine,
breccia; polished section, •PLATE VI.
Fro. 7. l~seudomorph of euhedral blende crystal (outlined in white), marginallyreplaced by chlorite; unreplaced core of blende (black) contains exsolved
ehalcopyrite. The surrounding rock is a shaly, dolomitic sandstone. Shallee
mine, 260-ft. level, borehole 39 at 45 ft. ; thin section with X-nicols, • 47.

Fro. 8. As for fig. 7. Unreplaced core of blende (white) surrounded by chlorite(medium grey). Irregular masses of light yellow blende (white) have replacedrock groundmass around pseudomorph. Copper-rich blende replaced by chlorite
was redeposited nearby purged of inclusions. Shallee mine, 260-ft. level,
borehole 39 at 45 ft. ; polished section, • 47.
Fro. 9. Feathery plates of sericite (black) surrounded by galena (white) in a narrowvein, between sandstone wall-rocks. Shallee mine, borehole 2E at 12.5 ft.;polished section, • 67.
Fzr 10. Relic texture in centre of pyritic spherulite indicating former presence ofclump of marcasite crystals. Knockanroe miIm, 'Sulphur Lode'; polishedsection, • 51.