descriptive mineralogy of pugh quarry, northwestern ohio

DESCRIPTIVE MINERALOGY OF PUGH QUARRY,NORTHWESTERN OHIO: MARCASITE AND PYRITE1

DAVID F. PARR2 and LUKE L. Y. CHANG, Department of Geology, Miami University, Oxford,OH 4505G

Abstract. Minerals from solution cavities and associated collapse breccias in theMiddle Devonian dolostone at Pugh Quarry, Wood County, Ohio were collected andidentified. Two types of marcasite were recognized: banded encrustations and euhedralcrystals. The banded marcasite is widespread in the mineral zone, especially in thenortheastern section of the Quarry, and showed 3 distinct habits: subhedral, globular,and columnar. On freshly exposed surfaces, the colors were greenish gray or a mix-ture of pale yellow and gray. A characteristic of the banded marcasite is the presenceof extensive intergrowth twinning. The euhedral marcasite was found in rocks in allparts of the Quarry, both inside and. outside the mineral zone. On freshly brokensurfaces, the euhedral crystals were gray-white with a greenish cast. Prismatic andtabular habits were observed. Many of the crystals showed hopper development.Pyrite is not a common mineral in Pugh Quarry. Generally, crystals were small, lessthan 1 mm in size, greenish brown to yellowish brown in color, and highly lustrous.

OHIO J. SCI. 77(5): 213, 1977

Museums and private mineral collec-tions throughout the U.S. and othercountries display crystal specimens ofcarbonate, sulfate, and sulfide mineralsfrom quarries in the Paleozoic carbonaterocks in the mid-western United States.Occurrence of these minerals has beenpreviously reported (Kraus 1905; Fordand Pogue 1909; Morrison 1935; Howard1951), but little work has been done ontheir descriptive mineralogy. It is thepurpose of this study to provide a de-tailed investigation of the mineral as-semblages in the carbonate rocks at PughQuarry, which is located in the SW]^,SWM, Sec. 6, T.4N., R.9E. in MiltonTownship, Wood Co., Ohio. In this re-port, marcasite and pyrite are described.Methods used for investigation in thisstudy included megascopic identification,microscopic examination of thin sectionsand polished sections, reflecting gonio-metric measurement, and x-ray powderdiffraction studies.

Manuscript received June 24, 1976 and in finalrevised form May 3, 1977 (#76-54).

2Present Address: Department of Geology,Wisconsin State University, Superior, Wis-

MINERAL OCCURRENCEThe stratigraphy at Pugh Quarry is

shown in figure 1. Wisconsin age till andlacustrian sands form the overburden atPugh Quarry. Glacial grooves and stria-tions were exposed on the bedrock aroundthe quarry rim where the overburden hadbeen stripped back. Stylolites occurredin the strata exposed at Pugh Quarry.Petroliferous black shale seams approxi-mately 6 mm thick separated the rocksabove and below stylolites, and brec-ciation was common.

Marcasite, pyrite, and 6 other mineralsoccurred in rocks at Pugh Quarry (table1). The minerals were generally re-stricted to a zone (referred to hereafteras the mineral zone) consisting of nearlycontinuous bands of cavities about 9 cmthick located in the upper 18 to 24 cmof the Anderson Formation of the De-troit River Group (see fig. 1). Breccia-tion in this mineral zone locally resembledcollapse phenomena associated with areasof cavern development. It was similar tothe brecciation described by Jackson andBeales (1967) in ore zones of the Okla-home-Kansas-Missouri Tri-State MiningDistrict. The breccias in both cases

213

214 D. F. PARR AND L. L. Y. CHANG Vol. 77

DundeeLimestone

Unit 8

disconformity

Unit 7

Unit 6

Unit 5

Unit 4

Unit 3

Unit 2

SylvaniaSandstone

Unit I

Janssens, 1970p. 2 ,22

15'Overburden

A

28'

V

Dolomite-light 8 medium brownto very light brownish gray,sandy, bedded to massive,finely sucrosic with goodintercrystalline porosity.Nodular fossiliferous chertin upper portion of unit.

Dolomite- very Iight gray very lightand light brown dolomicnte gradinginto dolosiltite, stromatoliticlaminations in lower half.

3-6'Stromatolitic doiomicrite-dolosiitite,

brecciated mineralized zone.

J Dolomite-light brownish graydolosiltite with interbedded dolo-micrite, massive with poorvugqy porosity.

2 -5 ' Dolomite-stromatolitic dolosiltite

A Dolomite-light grayish brown to•7.5' dark brown dolosiltite.

A

28

V

Dolomite-light 8 medium browndolosiltite with interbeddeddolomicnte, stromatoliticstructures, and vuggy porosity.

A

ISandstone-fine to medium quartz

sand with rounded 8 frosted groins.

Forsyth,p. 20

ADolomite —light gray to dork

brownish groy, sugarytexture, petroliferous,fossiliferous zones, andchert nodules in upperpart.

Dolomite —brown, verydense, thin-bedded,locally conglomeratic.

Contains large calcitecrystals and smallcrystals of f luor i te,celestite, pyrite, andmarcasite.

Dolomite— brown to darkbrown, fine groined,relatively thick bedded.

Sandstone-fine grainedrounded quartz grainsrelatively thin andeven bedded.

A

15

A

50

t10

i

DundeeLimestone

AnderdonDolomite

LucasDolomite

AmherstbergDolomite

SylvaniaSandstone

FIGURE 1.(1970).

Columnar section of rocks exposed at Pugh Quarry after Forsyth (1966) and Janssens

DE

TR

OIT

R

IVE

R

GR

OU

P

Ohio J. Sci. MARCASITE AND PYRITE FROM PUGH QUARRY 215

FIGURE 2. Bio-laminar dolostone. The highly porous character of the rock and the wavylaminations are interpreted as stromatolitic in origin. X 0.4

FIGURE 3. Bio-laminar dolostone. The structure may be the remains of a coral organism.Note the areas of marcasite replacement. Actual size.

FIGURE 4. Polished section, one nicol, marcasite (light) and dolomite (dark). Sharp rhombsof dolomite are enclosed in the pore space filling marcasite. X 74

FIGURE 5. Thin section, one nicol, marcasite (dark) and dolomite (light). Sharp rhombs ofdolomite are enclosed in pore space filling marcasite. X 60


were cemented by accessory minerals.The specimens used in this study weredeposited in the Department of Geology,Miami University, Oxford, Ohio.

TABLE 1Minerals Identified from Pugh

Quarry, Listed by ChemicalGroup

Chemical Group

Sulfides

Carbonates

HalideSulfates

Minerals

MarcasitePyriteSphaleriteCalciteDolomiteFluoriteBariteCelestite

MARCASITEMarcasite was a common mineral in the

carbonate rocks at Pugh Quarry. Twotypes were recognized: euhedral crystalsand banded encrustations. In this studythe term euhedral was used for anycrystal which was bounded by crystalsurfaces except, perhaps, for the point ofattachment to the carbonate rock. Mar-casite consisting of solid coatings of in-tergrown aggregates of radiating orcolumnar crystals was considered to bebanded marcasite.

BANDED MARCASITE

Banded marcasite was widespread inthe mineral zone, especially in the north-eastern section of the quarry. Singlebands as much as 5 mm thick were foundin this area, particularly in portions ofthe mineral zone showing strong brec-ciation. In places, marcasite served asthe cementing agent between clasts inbreccias.

Relation to Host Rock: Dolostones onwhich the banded marcasite occurredwere oolite, structureless rocks with uni-form sized crystals, or bio-laminar (Bio-laminar is a general term for those whosestructures represent algal stromatolites,stromatoproids, or corals). The dolo-stones were recrystallized; individualcrystals were 0.5 mm or less in maximumdimension (fig. 2 and 3).

Polished section and thin section ex-aminations showed that marcasite porefilling was prevalent in all of the rockswhere marcasite had a banded habit.Euhedral dolomite crystals were enclosedtotally or in part by marcasite. Therewas no indication that the developmentof the marcasite in any way interferedwith the recrystallization of the dolomite,indicating an antecedent relationship ofthe dolomite to the marasite (fig. 4 and5).

Several specimens had oolite structuresassociated with thick banded marcasite.The oolite structures were most distinctalong the marcasite-dolostone interfaces,which were characterized by marcasitefilling of spaces between oolite (fig. 6).

FIGURE 6. Polished section, one nicol, mar-casite (white) replacing schalenblendesphalerite (light gray) on recrystallizeddolomite oolites (dark gray). X 32

Color: The surface of most bandedmarcasite from Pugh Quarry was dis-colored to a reddish brown due to oxida-tion. Freshly exposed surfaces weregreenish gray or a mixture of pale yellowand gray. Irridescent colors, dominantlyblues and blue-greens, were characteristicof the natural fracture surfaces of thebanded marcasite.


Habit: The banded marcasite showed 3distinct habits: subhedral, globular, andcolumnar. The columnar and globularhabits were dominant in the very thickmassive occurrences of the marcasitebands at Pugh Quarry. The subhedralhabit, generally in bands less than 5 mmthick, was made up of elongated indi-vidual crystals which were intergrownand formed a solid band of marcasite(fig. 7). The globular habit was char-acterized by thick encrusting bands ofmarcasite composed of intergrown crys-tals which radiated outward from a com-mon center, joining together to formcauliflower-like masses (fig. 8).

The columnar habit, the other maingrouping into which a large number ofPugh Quarry banded marcasites wereplaced, was a habit in which elongatedcrystals were intergrown in a near-parallel number of produce the columnarappearance. The direction of growth ofthe columnar crystals was perpendicularto the plane of the band in which theyoccurred. The band of marcasite formedon a given specimen was generally of eventhickness, 5 to 50 mm. Small calcitecrystals were seen on the surface of theband, and remnant blebs of schal en-blende sphalerite concentrated in hori-zons were present in the marcasite.Large, though generally rough, crystalterminations were common to the speci-mens of the columnar banded habit ofmarcasite.

Several of the marcasite band struc-tures showed crystal terminations onboth sides of the band (fig. 9) with op-posite sides showing dissimilar crystals.The side of the band toward the opencavities was covered by the large crudecrystal terminations and the reverse sidewas characterized by the presence ofsmall, sharp, nearly euhedral crystals.The interstices between these smallcrystals were filled with dolostone frag-ments. Other habits which were ob-served in marcasite collected from thestudy area were stalactitic crystal ag-gregates and stellate twins. These ha-its were rare (fig. 10).

Crystal Form: Positive identification toforms present as terminations of bandedmarcasite was not possible for several

reasons. A characteristic of the bandedhabit of marcasite was the presence ofextensive intergrowth twinning. This,combined with the brittle nature of thecrystal, made the separation of individualterminated crystal very difficult. Sev-eral terminated fragments were separatedfrom the band and mounted on the gonio-meter. When attempts were made tomeasure <£ and p angles, it was found thatthe crystal faces lacked the smoothnessand reflectivity necessory to produce animage could be used for measurement.An additional problem encountered inidentifying the crystal terminations fromthe banded marcasite was the degree towhich the crystals had been affected byoxidation. Most of the crystal surfaceson the terminations were sufficientlyweathered to preclude their use.

The crystal forms present on the termi-nations of the banded habits of marcasiteappeared to be similar to those identifiedon the crystals of the euhedral habit ofmarcasite. This was, for the most part,a comparative observation.

Alteration: Virtually all marcasite crys-tal surfaces showed alteration featureswhen collected. The dominant featureswere brown coatings and irridescenttarnish films. The brown coating wasprobably a limonite mineral. A whitepowder, found in association with marca-site on several specimens after storagefor some time in dump places, was ex-amined by x-ray powder diffraction.Results suggested that it was composedof hydrated iron sulfates, rozenite(FeSO4-4H2O) and szomolnokite (FeSO4-H2O).

EUHEDRAL MARCASITE

Individual euhedral crystals of marca-site were found in rocks in all parts of thequarry both inside and outside the min-eral zone. The Dundee Formation, abovethe Anderson Formation (fig. 1), con-tained cavities which resembled externalmolds of organisms. These openingscommonly contained small euhedral mar-casite crystals accompanied by small dolo-mite and fluorite crystals (fig. 11).

Below the mineral zone, marcasitecrystals also were found in the algalstromatolitic dolostone of the LucasFormation. Associated with the eu-


FIGURE 7. Marcasite (dark crystals) and sphalerite (light spherules) on dolostone. The individual marcasite crystals havegrown together to form a solid band of marcasite. Note the hemispherical bodies of sphalerite and the isolated euhedralmarcasite crystals. X 2FIGURE 8. Marcasite, globular type, with coating of finely crystalline calcite. Note the cauliflower-like appearance of themarcasite mass. X 0.3FIGURE 9. Marcasite on dolostone. Note the development of marcasite crystal terminations at the dolostone interaceX3.8FIGURE 10. Marcasite, euhedral crystals, on brecciated dolostone. These crystals represent the stellate fiveling habit ofmarcasite. X 3


hedral marcasite crystals were numerousminute crystals of marcasite and sphale-rite.

Relation to Host Rock: Two types of in-terface relationships were recognizedbetween euhedral marcasite crystals andthe dolostone host rock. The first typewas that crystals occurred as distinct in-dividuals scattered on the walls of cavi-

ties of the host rock. Megascopically,these crystals seemed to be glued to thesurface of the dolostone (fig. 12). Thesecrystals were commonly attached to thedolostone along only one crystal face, theremaining faces being free from impinge-ment. Typically, these faces were, as aresult, well developed.

In the second type of contact, crystals

• • . .

FIGURE 11. External mold of crinoid stem plate, small crystals of marcasite, fluorite,and dolomite are contained in the opening. X 2FIGURE 12. Euhedral marcasite crystals on dolostone. X 3.5FIGURE 13. Single euhedral crystal of marcasite showing hopper development on 101faces. A small reentrant angle marking the location of the twin plane, 101, in thecrystal can be seen. The pseudobipyramidal appearance of the crystal is apparentX 10FIGURE 14. Euhedral marcasite crystal. The small face commonly associated withtwinned euhedral crystals is shown. X 10FIGURE 15. Euhedral marcasite crystal. The small face commonly associated withtwinning on euhedral crystals, hopper development of faces at the center of crystal,and pseudobipyramidal character of the four faces on the end of the crystal can be seenX 10


of marcasite were removed from thedolostone with little difficulty, leavingbehind a well formed "external mold" ofthe crystal faces. The relation betweenthe host rock and the marcasite crystalwas similar to that between an internalmold and external mold of an organismafter the shell was removed.

Color: Euhedral marcasite was morecolorful than banded marcasite. Thecolors observed on the crystal faces werecaused by an oxidation coating. Whenexamined at arm's length, the color ofthe crystals appeared to be an olivebrown in daylight. Upon closer exami-nation, it became apparent that therange of colors covered the entire spec-trum, although green was dominant.On freshly broken surfaces, these crys-tals were grey-white with a greenish cast.

Habit: Euhedral marcasite exhibitedprismatic and tabular habits. Many ofthe crystals showed hopper development(fig. 13). Prismatic crystals were prev-alent. Crystals of this habit closely re-sembled octahedra with small cube modi-fications, but angular parameters of theseshowed them to be orthorhombic (fig. 12).

Two generations of marcasite growth,possibly more, were indicated by thepresence of hopper crystals. The finalstage of growth was notably more rapidthan that of the earlier stages. Hopperdevelopment on the (010) and (001)faces of marcasite was attributable tothe greater energies released by ions at-taching to the edges and corners of acrystal than those attaching to the faces(Grigor'ev 1961). Once the process ofovergrowth began, it perpetuated itselfdirectionally along the edges of a crystalbefore growing appreciably in towardsthe center of the crystal face (fig. 14 and15). This type of overgrowth indicateda period of rapid crystal development.

Variation in the dimensions of thebanded marcasite was found to be great.This was not found to be the case with theeuhedral marcasite, with 4 mm being themaximum dimension for any euhedralcrystal. No minimum dimension wasestablished; however, it was noted thatmost of these crystals fell within the 1to 3 mm range.

Crystal Form: Euhedral crystals wereexamined with a binocular microscope(20X), and 5 well developed crystalswere selected for measurements of phi (4>)and rho (p) values between their crystalforms. For {101} <j> had a constantvalue of 90° (90°, Palache et al 1944, p.313) and p varied from 52° to 52°45'(52°41'). For {110} 0 varied from 47°to 51° (50°40') and p had a constantvalue of 90° (90°). For {011} 0 was0° (0°) and p varied from 32°30' to 34°(31°59'). For {010} <p was 0° (0°) andp was 90° (90°).

Twinning on {101} was present innearly all of the euhedral crystals andwas readily apparent in polished sections.A {011} twin plane had also been re-ported for marcasite (Palache et al 1944),but no evidence for this type of twinningwas found in the Pugh Quarry specimensexamined.

On many of the crystals {101} facespredominated and characteristicallyshowed the hopper growth discussedabove. Step growth and pitting werealso present on faces of this form, butvicinal faces did not tend to develop.There was commonly unequal develop-ment of the different faces of this form.The development of the (101) was similarto that of the (ToI), and (To i) developedsimilar to (uT). Commonly the (101)—(ToI) face pair was significantly largerthan the (To i)-(ToT) face pair. The twinplane generally bisected the crystals, andthe associated re-entrant angles com-prised the (Toi) and (ioT) faces.

On the basis of their different </> and pvalues, {011} prisms were distinguishablefrom {110} prisms. Striations parallelwith the [100] axes and the presence ofred-brown to yellow-brown oxidationcoating were common to {011} prisms.All faces of this form tended to be de-veloped equally. Both the prominantstriations and the red-brown, yellow-brown oxidation coating of the {011}prisms were lacking on {110} prisms.Vicinal faces, step growth, and triangulargrowth pits were found on the {110}prism faces of many crystals. Positiveand negative faces of {110} prims weredeveloped equally.

The only pinacoid found on the crystalsexamined was {010}. Characteristically,


the {010} faces were among the largerfaces developed on these crystals. Par-allel growth, vicinal face development,and the presence of numerous high order{hkO} prisms all contributed to curvedsurfaces and the generally distorted na-ture of this form. On many crystals the{010} surfaces were so poor that noreliable angular measurements could bemade utilizing this form.

The combination of the 4 forms, {101}twinning, and the nature of developmentof the various forms all contributed tocrystals with habits which were deceiv-ingly simple in appearance. Faces ofthe {011} and {110} prisms were com-monly of equal area. In many cases thetwinning had resulted in a situationwhere all 4 faces of one prism form oc-curred on the same end of the crystal.The appearance of this was exactly thatof a bipyramid, distinguishable only onthe basis of </> and p measurements.Even when the prism faces were cor-rectly positioned, the resemblance be-tween the {110} and {011} forms was soclose that the 4 faces collectively re-sembled a bipyramidal form (figs. 12, 13,and 15). No true pyramid faces wereobserved on any of the euhedral crystals.Faces of one or both of the bipyramidalforms ({111} or {122}) may have beenpresent on the terminations of thebanded marcasite discussed earlier, but itwas not possible to identify them posi-tively. The dominant forms which con-trol led the habits observed on the PughQuarry marcasite were the {010} pinacoidand {101} prism.

PYRITEPyrite was not a common mineral in

Pugh Quarry. Generally, crystals weresmall, less than 1 mm in size, greenishbrown to yellowish brown in color, andhighly lustrous. The octahedorn, {111},was the predominant form. The apicesof the octahedra were truncated by smallpyritohedra, {102} (fig. 16), whichshowed characteristic twinning striations.The {011} form was also present on someof the crystals. Suggestions of the cube,{100}, were observed but positive identi-fication of this form could not be made.

A curious growth feature observed onmost of the pyrite crystals consisted of

reentrant angles occurring at the inter-section line of the octahedral crystalfaces. These angles did not coincidewith the twin laws of pyrite and wereinterpreted here as growth features, pos-sibly representing a second generation ofpyrite. The central portions of alloctahedral crystal faces were pitted.The bounding faces of these pits con-sisted of pyritohedral surfaces.

FIGURE 16. Pyrite on dolostone. Octa-hedral and pyritohedral crystal forms arevisible. X 5

The characteristic used to distinguishpyrite from marcasite in polished sectionexamination was its anomalous aniso-tropism under cross nicols (Ramdohr1969). Marcasite, and particularly PughQuarry marcasite, exhibits extremelystrong anisotropism accompanied byvivid interference colors. In plane po-larized lights pyrite is pale yellow tocreamy yellow, whereas marcasite isnearly white. The reflectivities of the 2minerals are essentially identical.

Acknowledgments. The authors are indebtedto Dr. James Bever, Miami University, for hiskind assistance and advice, to Dr. Charles


Kahle, Bowling Green State University, forseveral discussions, and to the Pugh QuarryCompany and Mr. Miller for their cooperation.Special thanks go to Mr. and Mrs. ClaytonWelch, Mr. Stan Esbenshade, Mr. CharlesDetrich, and Mr. Larry Hargrove, who do-nated and lent specimens to us for study.

LITERATURE CITEDFord, W. E. and J. L. Pogue 1909 Calcite

crystals from Kelley's Island, Lake Erie.Amer. J. Sci. 28: 186.

Forsyth, J. L. 1966 The geology of the Bowl-ing Green area, Wood County, Ohio. TheCompass 43: 202-214.

Grigor'ev, D. P. 1961 Ontogeny of Minerals.English transl. by Israel Program for Sci-entific Translations, Jerusalem, 1965. 250 p.

Howard, C. L. H. 1951 Celestite and fluoritefrom Clay Center, Ohio. Cleveland MuseumNatural History, Museum News 1: 125-130.

Jackson, S. A. and F. W. Beales 1967 Anaspect of sedimentary basin ecolution: theconcentration of Mississippi Valley-type oresduring late stages of diagenesis. Bull. Can.Petrol. Geol. 7: 751-763.

Janssens, A. 1970 Middle Devonian forma-tions in the subsurface of northwestern Ohio.State of Ohio Dept. Nat. Resour. Rept.Invest. 78, 22 p.

Kraus, E. H. 1905 Occurrence and distribu-tion of celestite bearing rocks. Amer. J. Sci.19: 286-293.

Morrison, R. B. 1935. The occurrence andorigin of celestite and fluorite at Clay Center,Ohio. Amer. Mineral. 20: 780-790.

Palache, C , H. Berman and C. Frondel 1944System of Mineralogy, 7th ed. John Wileyand Sons, New York, Vol. 1, 834 p.

Ramdohr, P. 1969. The Ore Minerals andTheir Intergrowths. Pergamon, London,1169 p.

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descriptive mineralogy of pugh quarry, northwestern ohio

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