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Epidote from the Zard Mountains, Kharan, Balochistan, Pakistan

Last Updated: 24th Jul 2013

Epidote from the Zard Mountains, Kharan, Balochistan, Pakistan



Michael E. Brownfield, Heather A. Lowers, and William K. Betterton
U.S. Geological Survey, Denver, CO 80225

INTRODUCTION

The authors received two unusual crystals of epidote from Rock Currier, Jewel Tunnel Imports, in 2012. The mineral specimens were collected at Zard Mountain (Zard Koh), in the central part of the Ruskoh Mountains (Rusk Koh), west of Kharan, Balochistan, Pakistan (written communication, Rock Currier, 2013). The epidote locality was most likely discovered in 2010.

These epidote crystals were unusual in both form and composition. The large crystals were flat tabular and pseudohexagonal in shape which is an uncommon crystal form for a monoclinic mineral (fig. 1). Other specimens from the same locality have been described as pseudo-octahedral in shape. The two crystals range in size from 5.5 to 6.5 centimeters (2.2 to 2.6 inches) and are slightly magnetic. The epidote crystals have a core matrix that resembles a weathered igneous rock. Some micro brown- to reddish-titanite crystals were observed under a binocular microscope on the surface and core areas of the crystals (figs. 2 and 3). Other minerals observed in the core areas include feldspar, biotite, and quartz. The crystals display evidence of cluster-growth with points of attachment to other crystals. The epidotes were most likely collected in pockets of a weathered igneous-skarn deposit.


Figure 1. Epidote crystal from Zard Mountain near Kharan, Balochistan, Pakistan. Specimen is about 2.5 cm (2.6 inches) in length. Rock Currier, Jewel Tunnel Imports, Los Angeles, Calif., supplied the epidote specimen.



Figure 2. Reflected-light (binocular) image of the core matrix of an epidote crystal from Zard Mountain near Kharan, Balochistan, Pakistan. Largest titanite crystal is about 0.1 mm. Rock Currier, Jewel Tunnel Imports, Los Angeles, Calif., supplied the epidote specimen. F, feldspar; Q, quartz; T, titanite.

Figure 3. Reflected-light (binocular) image of the core matrix of an epidote crystal from Zard Mountain near Kharan, Balochistan, Pakistan. Biotite crystals are about 0.2 mm. Rock Currier, Jewel Tunnel Imports, Los Angeles, Calif., supplied the epidote specimen. B, biotite; F, feldspar; Q, quartz; T, titanite.


X-RAY DIFFRACTION ANALYSIS

Mineralogy of the epidote crystals including the core matrix was determined by X-ray diffraction (XRD) methods. Samples were crushed and ground with an agate mortar and pestle and then sieved at 40 mesh. The sample was then micronized using a McCrone Micronizing mill to an average particle size ranging from 1 to 10 microns. XRD analyses of magnetic and nonmagnetic samples were performed on a PANalytical “X’Pert Pro–MPD” X-ray diffractometer in Bragg-Brentano geometry with nickel-filtered Cu K radiation (1.5418 Å wave length). The samples were spun and run from 5° to 80° 2 theta with a 0.0167° stepping increment, a dwell time of 400 seconds (4 hour total run time), with 1/8-degree fixed slits, and a 10-mm beam mask. XRD data were collected digitally and analyzed with Materials Data Inc. (MDI), Livermore, Calif., software and the International Centre for Diffraction Data Powder Diffraction File (PDF-4) database (International Centre for Diffraction Data, 2012) and National Institute of Standards and Technology “FIZ/NIST Inorganic ICSD” structure database (National Institute of Standards and Technology, 2012).

Quantitative mineral data on the epidote samples were collected digitally with MDI software and analyzed using Rietveld refinement quantitative XRD methods using the MDI “Whole Pattern Fit” software option for “Jade” (Bish and Howard, 1988; Young, 1995; McCusker and others, 1999). Samples were analyzed on a Phillips Diffractometer using Cu K radiation scanned at 20° to 80° 2 theta with a 0.03 stepping increment and a 2-second count scan rate.

MICROBEAM ANALYSIS

Magnetic and nonmagnetic splits of the epidote were prepared and analyzed by microbeam methods using a scanning electron microscope (SEM). The samples were prepared as polished epoxy-bound sections of the magnetic and nonmagnetic splits.

The polished epoxy-bound sections of the magnetic and nonmagnetic splits were imaged using a SEM with secondary electron imaging (SEI) and backscattered electron imaging (BEI) and assisted by semiquantitative energy dispersive spectral (EDS) analysis. Energy dispersive analyses allowed the calculation of cation ratios and element contents in the observed phases in the epidote samples. Heavier elements, such as iron, are brighter in the backscattered electron images.

X-RAY DIFFRACTION RESULTS

X-ray diffraction patterns of the magnetic and nonmagnetic splits are shown in figures 4, 5, 6, and 7. X-ray diffraction analysis of the epidote magnetic split (figs. 4 and 5) revealed major epidote with minor and trace amounts of magnetite, titanite, quartz, biotite, and chamosite (chlorite group). X-ray diffraction analysis of the nonmagnetic epidote split (figs. 6 and 7) revealed epidote with minor and trace amounts of titanite, quartz, albite, and actinolite.


Figure 4. X-ray diffractogram of the magnetic epidote split from Zard Mountain (Zard Koh), in the central part of the Ruskoh Mountains (Rusk Koh), west of Kharan, Balochistan, Pakistan.

Figure 5. Rietveld X-ray analysis report of the magnetic epidote split from Zard Mountain (Zard Koh), in the central part of the Ruskoh Mountains (Rusk Koh), west of Kharan, Balochistan, Pakistan.



Figure 6. X-ray diffractogram of the nonmagnetic epidote split from Zard Mountain (Zard Koh), in the central part of the Ruskoh Mountains (Rusk Koh), west of Kharan, Balochistan, Pakistan.

Figure 7. Rietveld X-ray analysis report of the nonmagnetic epidote split from Zard Mountain (Zard Koh), in the central part of the Ruskoh Mountains (Rusk Koh), west of Kharan, Balochistan, Pakistan.


Rietveld X-ray diffraction quantitative analysis conducted on the magnetic split confirmed that epidote (77.5 percent) was the predominant phases with 7.8 percent magnetite and 5.2 percent titanite (table 1); whereas the nonmagnetic spit contained 88.3 percent epidote and 8.1 percent titanite (table 1).

Table 1. Quantitative mineralogy of magnetic and nonmagnetic epidote splits from Zard Mountain, in the central part of the Ruskoh Mountains, west of Kharan, Balochistan, Pakistan, determined by Rietveld X-ray diffraction analysis. Values are given in percent.
[nd, not detected]


Table 1



MICROBEAM ANALYSIS RESULTS

Microbeam methods support the mineralogical identifications obtained by X-ray diffraction methods. Scanning electron microscope backscattered electron images of the nonmagnetic epidote split confirmed the occurrence of titanite inclusions in the epidote (fig. 8). Zoning was evident in the electron images resulting in minor differences in the iron content of the epidote (figs. 8, 9, and 10). Microcrystalline inclusions in the titanite were also imaged (figs. 8 and 10). SEM backscattered electron images of the magnetic epidote confirmed the occurrence of magnetite and titanite (figs 11, 12, and 13). Chamosite was also confirmed in the magnetic split (fig. 13). Zoning within the epidote was also imaged in the magnetic and nonmagnetic splits (figs. 8, 9, 10, 11, and 12).


Figure 8. Scanning electron microscope (SEM) backscattered electron image from the nonmagnetic epidote split. Image shows zoning within the epidote resulting from minor differences in iron content. Bright-white microcrystals of magnetite are visible as inclusions in some titanite crystals. E, epidote; M, magnetite; T, titanite.

Figure 9. Scanning electron microscope (SEM) backscattered electron image from the nonmagnetic epidote split. Image shows zoning within the epidote resulting from minor differences in iron content. E, epidote; T, titanite.



Figure 10. Scanning electron microscope (SEM) backscattered electron image from the nonmagnetic epidote split. Image shows zoning within the epidote resulting from minor differences in iron content. Bright-white microcrystal inclusions of magnetite are imaged in the lower right titanite crystal. E, epidote; T, titanite.10

Figure 11. Scanning electron microscope (SEM) backscattered electron image from the magnetic epidote split. Image shows minor zoning within the epidote in the upper part of the image resulting from minor differences in iron content. E, epidote; M, magnetite; T, titanite.



Figure 12. Scanning electron microscope (SEM) backscattered electron image from the magnetic epidote split. Image shows zoning within the epidote resulting from minor differences in iron content. E, epidote; M, magnetite; T, titanite.

Figure 13. Scanning electron microscope (SEM) backscattered electron image from the magnetic epidote split. E, epidote; M, magnetite; T, titanite.


SUMMARY

The slightly magnetic epidote crystals from Zard Mountain, Pakistan contain magnetite inclusions in their core material. This core material is a weathered igneous rock (skarn) that contains magnetite, titanite, quartz, albite, biotite, actinolite, and chamosite. The epidote crystals are found in pockets within the weathered igneous rock or skarn-like deposit.

ACKNOWLEDGMENTS

The authors thank Ronald C. Johnson and Timothy R. Klett for their suggestions and comments, which greatly improved the text. The authors would also like to thank Rock Currier, Jewel Tunnel Imports, Los Angeles, Calif. for supplying the epidote specimens.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

REFERENCES

Bish, D.L., and Howard, S.A., 1988, Quantitative phase analysis using the Rietveld method: Journal of Applied Crystallography, v. 21, no. 2, p. 86–91.

International Centre for Diffraction Data (ICDD), 2012, Powder Diffraction File, PDF-4: International Centre for Diffraction Data, Newtown Square, Pennsylvania.

McCusker, L.B., von Dreele, R.B., Cox, D.E., Lourer, D., and Scardi, P., 1999, Rietveld refinement guidelines: Journal of Applied Crystallography, v. 32, no. 1, p. 36–50.

National Institute of Standards and Technology (NIST), 2012, FIZ/NIST Inorganic Crystal Structure Database (ICSD): National Institute of Standards and Technology, Boulder, Colorado.

Young, R.A., 1995, editor, The Rietveld Method: International Union of Crystallography, Oxford University Press, Oxford, 298 p.









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Comments

Great work!!! Thanks so much for this.

Rob Woodside
29th Jul 2013 9:07pm
This was kindly posted on Facebook and gives locality info by Nauroz Nausherwani who collected there:

Nauroz Nausherwani Hello Rob ! Yes the Brookites and Anatase in Balochistan are from Zard(Balochi language word for Yellow color ) mountains and also found at Char Kohan (Balochi language word for 4 mountains )mountains. I have myself collected magnetic epidotes and are found at Maldeen,Raskoh Mountain not from zard mountains. As a collector and dealer for minerals of Balochistan , I never got/received/collected amethyst from Kharan district where zard and char kohan mountain is situated . I do received many fine amethyst( also some scepters with lapidocrocoite inclusions ) from Dalbandin Balochistan .

So these Epidotes are from Maldeen, Raskoh Mts, Balochistan, Pakistan.

Rob Woodside
30th Jul 2013 12:22am
Very informative report. Thank you
Rob Thank you for informing me about this report.

Nauroz Nausherwani

Nauroz Nausherwani
30th Jul 2013 11:28pm

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