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 the Middle Devonian dolostone at Pugh Quarry, Wood County, Ohio were collected and identified. Two types of marcasite were recognized: banded encrustations and euhedral crystals. The banded marcasite is widespread in the mineral zone, especially in the northeastern 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 presence of extensive intergrowth twinning. The euhedral marcasite was found in rocks in all parts of the Quarry, both inside and. outside the mineral zone. On freshly broken surfaces, the euhedral crystals were gray-white with a greenish cast. Prismatic and tabular habits were observed. Many of the crystals showed hopper development. Pyrite is not a common mineral in Pugh Quarry. Generally, crystals were small, less than 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- MINERAL OCCURRENCE tions throughout the U.S. and other The stratigraphy at Pugh Quarry is countries display crystal specimens of shown in figure 1. Wisconsin age till and carbonate, sulfate, and sulfide minerals lacustrian sands form the overburden at from quarries in the Paleozoic carbonate Pugh Quarry. Glacial grooves and stria- rocks in the mid-western United States. tions were exposed on the bedrock around Occurrence of these minerals has been the quarry rim where the overburden had previously reported (Kraus 1905; Ford been stripped back. Stylolites occurred and Pogue 1909; Morrison 1935; Howard in the strata exposed at Pugh Quarry. 1951), but little work has been done on Petroliferous black shale seams approxi- their descriptive mineralogy. It is the mately 6 mm thick separated the rocks purpose of this study to provide a de- above and below stylolites, and brec- tailed investigation of the mineral as- ciation was common. semblages in the carbonate rocks at Pugh Marcasite, pyrite, and 6 other minerals Quarry, which is located in the SW]^, occurred in rocks at Pugh Quarry (table SWM, Sec. 6, T.4N., R.9E. in Milton 1). The minerals were generally re- Township, Wood Co., Ohio. In this re- stricted to a zone (referred to hereafter port, marcasite and pyrite are described. as the mineral zone) consisting of nearly Methods used for investigation in this continuous bands of cavities about 9 cm study included megascopic identification, thick located in the upper 18 to 24 cm microscopic examination of thin sections of the Anderson Formation of the De- and polished sections, reflecting gonio- troit River Group (see fig. 1). Breccia- metric measurement, and x-ray powder tion in this mineral zone locally resembled diffraction studies. collapse phenomena associated with areas of cavern development. It was similar to Manuscript received June 24, 1976 and in final the brecciation described by Jackson and revised form May 3, 1977 (#76-54). Beales (1967) in ore zones of the Okla- 2Present Address: Department of Geology, Wisconsin State University, Superior, Wis- home-Kansas-Missouri Tri-State Mining District. The breccias in both cases 213 214 D. F. PARR AND L. L. Y. CHANG Vol. 77

Janssens, 1970 Forsyth, p. 2,22 p. 20

15' Overburden A Dolomite —light gray to dork brownish groy, sugary A texture, petroliferous, fossiliferous zones, and chert nodules in upper Dundee Dundee Dolomite-light 8 medium brown part. Limestone to very light brownish gray, Limestone sandy, bedded to massive, finely sucrosic with good intercrystalline porosity. Nodular fossiliferous chert Unit 8 28' in upper portion of unit.

Dolomite —brown, very A dense, thin-bedded, locally conglomeratic. Contains large calcite Anderdon crystals and small 15 Dolomite crystals of fluorite, celestite, pyrite, and disconformity V Dolomite- very Iight gray very light marcasite. and light brown dolomicnte grading into dolosiltite, stromatolitic Unit 7 laminations in lower half. Stromatolitic doiomicrite-dolosiitite, A Unit 6 3-6' brecciated mineralized zone.

Dolomite-light brownish gray Unit 5 dolosiltite with interbedded dolo- J micrite, massive with poor vugqy porosity. Unit 4 2-5' Dolomite-stromatolitic dolosiltite A Dolomite-light grayish brown to •7.5' dark brown dolosiltite. Unit 3 Dolomite— brown to dark brown, fine groined, Lucas relatively thick bedded. Dolomite A 50

Dolomite-light 8 medium brown dolosiltite with interbedded dolomicnte, stromatolitic Unit 2 28 structures, and vuggy porosity. DETROI T RIVE R GROU P

V Amherstberg Dolomite Sylvania A Sandstone-fine to medium quartz Sandstone-fine grained rounded quartz grains Sandstone sand with rounded 8 frosted groins. relatively thin and t Unit I even bedded. Sylvania I i10 Sandstone FIGURE 1. Columnar section of rocks exposed at Pugh Quarry after Forsyth (1966) and Janssens (1970). Ohio J. Sci. MARCASITE AND PYRITE FROM PUGH QUARRY 215

FIGURE 2. Bio-laminar dolostone. The highly porous character of the rock and the wavy laminations 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 rhombs of dolomite are enclosed in the pore space filling marcasite. X 74 FIGURE 5. Thin section, one nicol, marcasite (dark) and dolomite (light). Sharp rhombs of dolomite are enclosed in pore space filling marcasite. X 60 216 D. F. PARR AND L. L. Y. CHANG Vol. 77

were cemented by accessory minerals. Polished section and thin section ex- The specimens used in this study were aminations showed that marcasite pore deposited in the Department of Geology, filling was prevalent in all of the rocks Miami University, Oxford, Ohio. where marcasite had a banded habit. Euhedral dolomite crystals were enclosed TABLE 1 totally or in part by marcasite. There Minerals Identified from Pugh Quarry, Listed by Chemical was no indication that the development Group of the marcasite in any way interfered with the recrystallization of the dolomite, Chemical Group Minerals indicating an antecedent relationship of the dolomite to the marasite (fig. 4 and 5). Sulfides Marcasite Several specimens had oolite structures Pyrite associated with thick banded marcasite. Sphalerite Carbonates Calcite The oolite structures were most distinct Dolomite along the marcasite-dolostone interfaces, Halide Fluorite which were characterized by marcasite Sulfates Barite filling of spaces between oolite (fig. 6). Celestite

MARCASITE Marcasite was a common mineral in the carbonate rocks at Pugh Quarry. Two types were recognized: euhedral crystals and banded encrustations. In this study the term euhedral was used for any crystal which was bounded by crystal surfaces except, perhaps, for the point of attachment to the carbonate rock. Mar- casite consisting of solid coatings of in- tergrown aggregates of radiating or columnar crystals was considered to be banded marcasite.

BANDED MARCASITE Banded marcasite was widespread in the mineral zone, especially in the north- eastern section of the quarry. Single bands as much as 5 mm thick were found in this area, particularly in portions of the mineral zone showing strong brec- FIGURE 6. Polished section, one nicol, mar- ciation. In places, marcasite served as casite (white) replacing schalenblende the cementing agent between clasts in sphalerite (light gray) on recrystallized breccias. dolomite oolites (dark gray). X 32 Relation to Host Rock: Dolostones on which the banded marcasite occurred Color: The surface of most banded were oolite, structureless rocks with uni- marcasite from Pugh Quarry was dis- form sized crystals, or bio-laminar (Bio- colored to a reddish brown due to oxida- laminar is a general term for those whose tion. Freshly exposed surfaces were structures represent algal stromatolites, greenish gray or a mixture of pale yellow stromatoproids, or corals). The dolo- and gray. Irridescent colors, dominantly stones were recrystallized; individual blues and blue-greens, were characteristic crystals were 0.5 mm or less in maximum of the natural fracture surfaces of the dimension (fig. 2 and 3). banded marcasite. Ohio J. Sci. MARCASITE AND PYRITE FROM PUGH QUARRY 217 Habit: The banded marcasite showed 3 reasons. A characteristic of the banded distinct habits: subhedral, globular, and habit of marcasite was the presence of columnar. The columnar and globular extensive intergrowth twinning. This, habits were dominant in the very thick combined with the brittle nature of the massive occurrences of the marcasite crystal, made the separation of individual bands at Pugh Quarry. The subhedral terminated crystal very difficult. Sev- habit, generally in bands less than 5 mm eral terminated fragments were separated thick, was made up of elongated indi- from the band and mounted on the gonio- vidual crystals which were intergrown meter. When attempts were made to and formed a solid band of marcasite measure <£ and p angles, it was found that (fig. 7). The globular habit was char- the crystal faces lacked the smoothness acterized by thick encrusting bands of and reflectivity necessory to produce an marcasite composed of intergrown crys- image could be used for measurement. tals which radiated outward from a com- An additional problem encountered in mon center, joining together to form identifying the crystal terminations from cauliflower-like masses (fig. 8). the banded marcasite was the degree to The columnar habit, the other main which the crystals had been affected by grouping into which a large number of oxidation. Most of the crystal surfaces Pugh Quarry banded marcasites were on the terminations were sufficiently placed, was a habit in which elongated weathered to preclude their use. crystals were intergrown in a near- The crystal forms present on the termi- parallel number of produce the columnar nations of the banded habits of marcasite appearance. The direction of growth of appeared to be similar to those identified the columnar crystals was perpendicular on the crystals of the euhedral habit of to the plane of the band in which they marcasite. This was, for the most part, occurred. The band of marcasite formed a comparative observation. on a given specimen was generally of even Alteration: Virtually all marcasite crys- thickness, 5 to 50 mm. Small calcite tal surfaces showed alteration features crystals were seen on the surface of the when collected. The dominant features band, and remnant blebs of schal en- were brown coatings and irridescent blende sphalerite concentrated in hori- tarnish films. The brown coating was zons were present in the marcasite. probably a limonite mineral. A white Large, though generally rough, crystal powder, found in association with marca- terminations were common to the speci- site on several specimens after storage mens of the columnar banded habit of for some time in dump places, was ex- marcasite. amined by x-ray powder diffraction. Several of the marcasite band struc- Results suggested that it was composed tures showed crystal terminations on of hydrated iron sulfates, rozenite both sides of the band (fig. 9) with op- (FeSO4-4H2O) and szomolnokite (FeSO4- posite sides showing dissimilar crystals. H2O). The side of the band toward the open cavities was covered by the large crude EUHEDRAL MARCASITE crystal terminations and the reverse side Individual euhedral crystals of marca- was characterized by the presence of site were found in rocks in all parts of the small, sharp, nearly euhedral crystals. quarry both inside and outside the min- The interstices between these small eral zone. The Dundee Formation, above crystals were filled with dolostone frag- the Anderson Formation (fig. 1), con- ments. Other habits which were ob- tained cavities which resembled external served in marcasite collected from the molds of organisms. These openings study area were stalactitic crystal ag- commonly contained small euhedral mar- gregates and stellate twins. These ha- casite crystals accompanied by small dolo- its were rare (fig. 10). mite and fluorite crystals (fig. 11). Below the mineral zone, marcasite Crystal Form: Positive identification to crystals also were found in the algal forms present as terminations of banded stromatolitic dolostone of the Lucas marcasite was not possible for several Formation. Associated with the eu- 218 D. F. PARR AND L. L. Y. CHANG Vol. 77

FIGURE 7. Marcasite (dark crystals) and sphalerite (light spherules) on dolostone. The individual marcasite crystals have grown together to form a solid band of marcasite. Note the hemispherical bodies of sphalerite and the isolated euhedral marcasite crystals. X 2 FIGURE 8. Marcasite, globular type, with coating of finely crystalline calcite. Note the cauliflower-like appearance of the marcasite mass. X 0.3 FIGURE 9. Marcasite on dolostone. Note the development of marcasite crystal terminations at the dolostone interace X3.8 FIGURE 10. Marcasite, euhedral crystals, on brecciated dolostone. These crystals represent the stellate fiveling habit of marcasite. X 3 Ohio J. Sci. MARCASITE AND PYRITE FROM PUGH QUARRY 219 hedral marcasite crystals were numerous ties of the host rock. Megascopically, minute crystals of marcasite and sphale- these crystals seemed to be glued to the rite. surface of the dolostone (fig. 12). These Relation to Host Rock: Two types of in- crystals were commonly attached to the terface relationships were recognized dolostone along only one crystal face, the between euhedral marcasite crystals and remaining faces being free from impinge- the dolostone host rock. The first type ment. Typically, these faces were, as a was that crystals occurred as distinct in- result, well developed. dividuals scattered on the walls of cavi- 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 2 FIGURE 12. Euhedral marcasite crystals on dolostone. X 3.5 FIGURE 13. Single euhedral crystal of marcasite showing hopper development on 101 faces. A small reentrant angle marking the location of the twin plane, 101, in the crystal can be seen. The pseudobipyramidal appearance of the crystal is apparent X 10 FIGURE 14. Euhedral marcasite crystal. The small face commonly associated with twinned euhedral crystals is shown. X 10 FIGURE 15. Euhedral marcasite crystal. The small face commonly associated with twinning 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 seen X 10 220 D. F. PARR AND L. L. Y. CHANG Vol. 77 of marcasite were removed from the Crystal Form: Euhedral crystals were dolostone with little difficulty, leaving examined with a binocular microscope behind a well formed "external mold" of (20X), and 5 well developed crystals the crystal faces. The relation between were selected for measurements of phi (4>) the host rock and the marcasite crystal and rho (p) values between their crystal was similar to that between an internal forms. For {101} had a constant mold and external mold of an organism value of 90° (90°, Palache et al 1944, p. after the shell was removed. 313) and p varied from 52° to 52°45' (52°41'). For {110} 0 varied from 47° Color: Euhedral marcasite was more to 51° (50°40') and p had a constant colorful than banded marcasite. The value of 90° (90°). For {011} 0 was colors observed on the crystal faces were 0° (0°) and p varied from 32°30' to 34° caused by an oxidation coating. When (31°59'). For {010}

and p crystal than those attaching to the faces values, {011} prisms were distinguishable (Grigor'ev 1961). Once the process of from {110} prisms. Striations parallel overgrowth began, it perpetuated itself with the [100] axes and the presence of directionally along the edges of a crystal red-brown to yellow-brown oxidation before growing appreciably in towards coating were common to {011} prisms. the center of the crystal face (fig. 14 and All faces of this form tended to be de- 15). This type of overgrowth indicated veloped equally. Both the prominant a period of rapid crystal development. striations and the red-brown, yellow- Variation in the dimensions of the brown oxidation coating of the {011} banded marcasite was found to be great. prisms were lacking on {110} prisms. This was not found to be the case with the Vicinal faces, step growth, and triangular euhedral marcasite, with 4 mm being the growth pits were found on the {110} maximum dimension for any euhedral prism faces of many crystals. Positive crystal. No minimum dimension was and negative faces of {110} prims were established; however, it was noted that developed equally. most of these crystals fell within the 1 The only pinacoid found on the crystals to 3 mm range. examined was {010}. Characteristically, Ohio J. Sci. MARCASITE AND PYRITE FROM PUGH QUARRY 221 the {010} faces were among the larger reentrant angles occurring at the inter- faces developed on these crystals. Par- section line of the octahedral crystal allel growth, vicinal face development, faces. These angles did not coincide and the presence of numerous high order with the twin laws of pyrite and were {hkO} prisms all contributed to curved interpreted here as growth features, pos- surfaces and the generally distorted na- sibly representing a second generation of ture of this form. On many crystals the pyrite. The central portions of all {010} surfaces were so poor that no octahedral crystal faces were pitted. reliable angular measurements could be The bounding faces of these pits con- made utilizing this form. sisted of pyritohedral surfaces. The combination of the 4 forms, {101} twinning, and the nature of development of the various forms all contributed to crystals with habits which were deceiv- ingly simple in appearance. Faces of the {011} and {110} prisms were com- monly of equal area. In many cases the twinning had resulted in a situation where all 4 faces of one prism form oc- curred on the same end of the crystal. The appearance of this was exactly that of a bipyramid, distinguishable only on the basis of and p measurements. Even when the prism faces were cor- rectly positioned, the resemblance be- tween the {110} and {011} forms was so close that the 4 faces collectively re- sembled a bipyramidal form (figs. 12, 13, and 15). No true pyramid faces were observed on any of the euhedral crystals. Faces of one or both of the bipyramidal forms ({111} or {122}) may have been present on the terminations of the banded marcasite discussed earlier, but it was not possible to identify them posi- tively. The dominant forms which con- trol led the habits observed on the Pugh Quarry marcasite were the {010} pinacoid FIGURE 16. Pyrite on dolostone. Octa- and {101} prism. hedral and pyritohedral crystal forms are visible. X 5 PYRITE Pyrite was not a common mineral in The characteristic used to distinguish Pugh Quarry. Generally, crystals were pyrite from marcasite in polished section small, less than 1 mm in size, greenish examination was its anomalous aniso- brown to yellowish brown in color, and tropism under cross nicols (Ramdohr highly lustrous. The octahedorn, {111}, 1969). Marcasite, and particularly Pugh was the predominant form. The apices Quarry marcasite, exhibits extremely of the octahedra were truncated by small strong anisotropism accompanied by pyritohedra, {102} (fig. 16), which vivid interference colors. In plane po- showed characteristic twinning striations. larized lights pyrite is pale yellow to The {011} form was also present on some creamy yellow, whereas marcasite is of the crystals. Suggestions of the cube, nearly white. The reflectivities of the 2 {100}, were observed but positive identi- minerals are essentially identical. fication of this form could not be made. Acknowledgments. The authors are indebted A curious growth feature observed on to Dr. James Bever, Miami University, for his most of the pyrite crystals consisted of kind assistance and advice, to Dr. Charles 222 D. F. PARR AND L. L. Y. CHANG Vol. 77

Kahle, Bowling Green State University, for Jackson, S. A. and F. W. Beales 1967 An several discussions, and to the Pugh Quarry aspect of sedimentary basin ecolution: the Company and Mr. Miller for their cooperation. concentration of Mississippi Valley-type ores Special thanks go to Mr. and Mrs. Clayton during late stages of diagenesis. Bull. Can. Welch, Mr. Stan Esbenshade, Mr. Charles Petrol. Geol. 7: 751-763. Detrich, and Mr. Larry Hargrove, who do- Janssens, A. 1970 Middle Devonian forma- nated and lent specimens to us for study. tions in the subsurface of northwestern Ohio. State of Ohio Dept. Nat. Resour. Rept. LITERATURE CITED Invest. 78, 22 p. Ford, W. E. and J. L. Pogue 1909 Calcite Kraus, E. H. 1905 Occurrence and distribu- crystals from Kelley's Island, Lake Erie. tion of celestite bearing rocks. Amer. J. Sci. Amer. J. Sci. 28: 186. 19: 286-293. Forsyth, J. L. 1966 The geology of the Bowl- Morrison, R. B. 1935. The occurrence and ing Green area, Wood County, Ohio. The origin of celestite and fluorite at Clay Center, Compass 43: 202-214. Ohio. Amer. Mineral. 20: 780-790. Grigor'ev, D. P. 1961 Ontogeny of Minerals. Palache, C, H. Berman and C. Frondel 1944 English transl. by Israel Program for Sci- System of Mineralogy, 7th ed. John Wiley entific Translations, Jerusalem, 1965. 250 p. and Sons, New York, Vol. 1, 834 p. Howard, C. L. H. 1951 Celestite and fluorite Ramdohr, P. 1969. The Ore Minerals and from Clay Center, Ohio. Cleveland Museum Their Intergrowths. Pergamon, London, Natural History, Museum News 1: 125-130. 1169 p.

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