Petrological Study on Sunstone: An Interdisciplinary Approach to Evaluate the Effect of Shodhana by Petrographic Thin Section Analysis

Dinesh Solanki*¹ Bharti Umretia²

1.        4th Semester PG Scholar, Upgraded Department of Rasashastra and Bhaishajya Kalpana, Government Ayurved College, Vadodara, Gujarat, India

2.        Reader and Head, Upgraded Department of Rasashastra and Bhaishajya Kalpana, Government Ayurved College, Vadodara, Gujarat, India

Correspondence: dineshsolanki8298@gmail.com

DOI: https://doi.org/10.71431/IJRPAS.2026.5804     

 INTRODUCTION

Rasashastra describes Suryakanta (Sunstone) as one of the six Uparatna (semi-precious gemstones) possessing therapeutic importance [1]Classical texts describe its Grahya Lakshana (desirable characteristics) as Vimala (pure), Nistusha (free from whitish streaks), Snigdha (smooth), Masrina (uniformly smooth texture), Nirvrana (free from pores), and the ability to exhibit a fiery appearance on exposure to sunlight [2]  These characteristics closely correspond with the mineral commercially known as Sunstone, which possesses a smooth surface, is free from pores, and exhibits a characteristic sparkling lustre due to light reflected from minute mineral inclusions. Based on these similarities, Sunstone has been considered the equivalent of classical Suryakanta.

Among the pharmaceutical procedures described in Rasashastra, Shodhana is an important purification process employed to eliminate physical impurities and improve the suitability of mineral substances for further pharmaceutical processing. Although the pharmaceutical processing of Suryakanta has been described in classical literature, there is limited scientific evidence regarding the structural modifications produced by purification. Petrography, a branch of geology concerned with the microscopic study of rocks and minerals using thin sections under a polarizing microscope, provides valuable information on mineral composition, crystalline texture, twinning, cleavage, grain boundaries, fractures, inclusions, and alteration features. Therefore, the present interdisciplinary study was undertaken to compare the petrographic characteristics of raw and purified Suryakanta (Sunstone) through thin-section analysis under a polarizing microscope and to scientifically correlate the microscopic observations with the classical pharmaceutical process.

MATERIALS AND METHODS

The present study was undertaken to evaluate the petrographic characteristics of Suryakanta (Sunstone) before and after the classical Shodhana (Purification) procedure. The study comprised procurement and authentication of the raw material, classical Shodhana, preparation of petrographic thin sections, and comparative petrographic examination of the the sample A (Raw) and sample B (Purified)

1. Procurement and Authentication of the Raw Material

A natural specimen of Suryakanta (Sunstone), belonging to the feldspar mineral group, was procured from an authentic gemstone dealer in Khambhat, Gujarat, India. The identity and authenticity of the specimen were confirmed by Neel Gem's Testing Laboratory [ISO 9001:2008 Certified], Ahmedabad, Gujarat, where the sample was examined and certified as natural Suryakanta (Sunstone) (Certificate No.: GS032545015593). Following authentication, the specimen was thoroughly cleaned with potable water to remove adhering dust and extraneous matter and was subsequently divided into two equal portions. sample A was retained as the Raw Sunstone, while the sample B was subjected to the classical Shodhana (purification) procedure for comparative petrographic evaluation.

2. Purification of Sunstone

             Purification of Sunstone was carried out according to the method described in Rasaprakashika, according to the classical reference, the Suryakanta (Sunstone) specimen was tied in a cloth pouch (Pottali) and suspended in freshly prepared Juice of Citrus Limon L. using the Dolayantra apparatus. The sample was subjected to boiling continuously for three Yamas (9 hours) under controlled heating [3] On completion of the procedure, the sample was removed from the apparatus, washed thoroughly with potable water to remove residual Juice of Citrus Limon L., air-dried at room temperature, and preserved for petrographic evaluation.

3. Preparation and Petrographic Examination of Thin Sections

Petrographic thin sections of both the sample A (Raw) and sample B (Purified) Sunstone samples were prepared in the Department of Geology (Petrology), The Maharaja Sayajirao University of Vadodara, Gujarat, following standard geological thin-section preparation techniques. Each specimen was cut into a suitable size, mounted on a glass slide using a suitable adhesive, and ground to a standard thickness of approximately 30 μm (0.03 mm). The prepared sections were subsequently polished and permanently mounted with a cover slip to facilitate examination under transmitted polarized light [4,5]

The prepared thin sections were examined using a MOTIC PM-28 Series Polarizing Microscope under Plane Polarized Light (PPL) and Cross Polarized Light (XPL). Comparative petrographic observations were carried out to evaluate mineralogical composition and textural characteristics, including crystalline texture, feldspar twinning, cleavage, fractures, grain boundaries, inclusions, and alteration features [6]. Representative photomicrographs of both the sample A (Raw) and sample B (Purified) both the sample A (Raw) and sample B (Purified) were recorded, and the observed petrographic characteristics were compared to assess the influence of the classical Shodhana procedure on the internal crystalline framework of Sunstone.

RESULTS AND DISCUSSION

Petrographic Observations [7]

Organoleptic observation: The purified sunstone showed a more uniform orange colour with better lustre and shine compared to the raw sunstone. The visible surface impurities were reduced, making the stone appear cleaner. In contrast, the raw sunstone exhibited a dull orange colour with less lustre and shine. The macroscopic appearance of the raw sunstone (Sample A) and purified sunstone (Sample B) is presented in Figure 1 and Figure 2, respectively.

A comparative petrographic examination of Raw and processed Suryakanta (Sunstone) thin sections was carried out under Plane Polarized Light (PPL) and Cross Polarized Light (XPL) using a MOTIC PM-28 Series Polarizing Microscope at 2.5× magnification. Representative photomicrographs are presented in Figures 3–10.

Figure 1. Raw sunstone (Sample A).                  Figure 2. Purified sunstone (Sample B).

 BEFORE SHODHANA

  Figure 3. Thin section under XPL.                         Figure 4. Thin section under PPL.

Figure 5. Thin section under XPL.                        Figure 6. Thin section under PPL.

   AFTER SHODHANA

Figure 7. Thin section under XPL.                        Figure 8. Thin section under PPL.

 Figure 9. Thin section under XPL.                      Figure 10. Thin section under PPL.

Table 1. Comparative Petrographic Observations of Raw and processed Suryakanta (Sunstone)

DISCUSSION

Shodhana is an important pharmaceutical procedure in Rasashastra intended to remove impurities and make mineral substances suitable for therapeutic use. The present study evaluated the influence of the classical purification procedure of Suryakanta using petrographic thin-section analysis under a polarizing microscope.

Comparative petrographic examination showed that the feldspar-dominated crystalline framework of Suryakanta (Sunstone) was preserved after Shodhana (purification). Although minor differences, such as comparatively cleaner grain boundaries and reduced opaque or inclusion-rich zones, were observed in the processed sample, no obvious disruption of the primary crystal framework was detected. These findings suggest that the classical pharmaceutical process produced only subtle microscopic changes.

A possible explanation for the limited petrographic differences observed between the Raw and purified Suryakanta is the nature of thin-section preparation. During petrographic analysis, the specimen is cut and ground to the standard thin-section thickness of approximately 30 µm, which removes the original external surface. Consequently, the earliest effects of purification, particularly those occurring at or near the mineral surface, may not be adequately reflected in the final thin section. Petrographic examination primarily evaluates the internal crystalline framework rather than surface morphology. Therefore, the minimal differences observed should not be interpreted as evidence that purification had no effect. Surface-sensitive techniques may provide a more appropriate assessment of the structural, morphological, and elemental changes induced by the classical Shodhana process.

A different methodological approach may be adopted in future studies by performing the Shodhana directly on the prepared petrographic thin section. Since the slide retains the exposed mineral surface, any surface modifications produced during purification may be observed more clearly under a polarizing microscope. This approach may provide better evidence of the microscopic changes induced by the classical Shodhana procedure.

The preservation of feldspar twinning and crystal morphology indicates that the prescribed purification procedure maintained the overall crystalline architecture of Suryakanta. The study also highlights the value of collaboration between Rasashastra and geological sciences in the scientific evaluation of Ayurvedic mineral drugs.

CONCLUSION

The present study demonstrated that classical Purification of Suryakanta using Juice of Citrus Limon L. in Dolayantra preserved the characteristic feldspar-dominated crystalline framework, with only subtle petrographic differences observed between the sample A (Raw) and sample B (Purified). Thin-section analysis proved useful for evaluating the internal microstructure, however the preparation process may limit the detection of initial purification-induced changes. Further investigations using complementary techniques such as SEM-EDS, XRD and XRF are recommended to comprehensively evaluate the effects of Purification.

CONFLICT OF INTEREST

The authors declare that they have no conflict of interest regarding the publication of this research. The study was conducted without any financial, commercial, or personal relationships that could have influenced the study design, data interpretation, or reporting of the results.

ACKNOWLEDGEMENT

The authors sincerely acknowledge the Department of Geology (Petrology), The Maharaja Sayajirao University of Vadodara, Gujarat especially Prof. Manoj Limaye, Mr. Gunjankumar Makwana, and Mr. Suryansh Gaur, for their valuable guidance and technical support in petrographic analysis.

REFERENCES

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3.    Bhishagvar Vaidya Shri Ramakrishna Sharma Dhandh, Rasaprakashika, Upratnavarnaniy 7/2, 1st edition, Shri Hanumanprasadji Khadiya Kishangad, Rajasthan, Pg no.151.

4.    Shelley D. Optical mineralogy. 2^nd edition, London: Chapman & Hall 1993 chapter: preparation of thin sections Pg no.15-24 

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