Baseline Study of Rock Samples Collected From Paleolithic Archaeological Site of Attirampakkam, Tamil Nadu

In the present work, rock samples have been collected from Paleolithic archaeological site Attirampakkam, Tamil Nadu, India to assess the presence of mineralogical composition of samples using Fourier Transform infrared-spectroscopic (FT-IR) technique and these identied minerals are conrmed by using X-Ray Diffraction (XRD) technique. From FT-IR spectra the presence of minerals such as quartz, orthoclase, microcline, kaolinite, montmorillonite, dolomite, aragonite, and palygroskite minerals are identied in rock samples. In this samples quartz is the majorly presented mineral and crystallinity index of quartz (SiO 2 ) is estimated for all the samples by comparing the ratio of intensity of the characteristic peak at 778 and 695 cm − 1 with the corresponding ratio for a standard sample. In rock samples, calculated crystallinity index of quartz is greater than 1 and shows that the disordered in nature. Additionally some more minerals such as hematite and rutile are identied in rock samples by X-ray diffraction technique. This extensive study shows that the archeological rock samples are wide variation in mineral composition.


Introduction
The crust of Earth is aggregated with different types of rocks. Rocks are made up of one or more minerals. These minerals are well known as rock-forming minerals. The Earth's crust is fully made up of minerals. Rocks and minerals are all around us, it plays a valuable role in the natural system. Naturally, rocks are classi ed into three types, according to how they formed such as (i) Igneous rocks, (ii) Sedimentary rock, (iii) Metamorphic rocks (Ravisankar et al., 2012 ). Igneous rocks are formed from the cooling and solidi cation of lava or magma. The sedimentary rocks are formed when compaction and cementation of the sediments.
When the rocks are changed as a result of exposure to intense heat and or pressure is well known as metamorphic rocks Dwellings of humans are made up of stone even travel to work on stone-paved roads. The archaeological study of rock is crucial for discovering human heritage because the stone has accompanied humans for millions of years, not only as a construction material, but also as a medium for the fabrication of tools, cult items, and jewelry (Szczepaniak, 2014). Much other evidence of previous civilizations (such as organic matters or oral tradition) degrade and are destroyed, therefore archaeological records are exceptionally rich in evidence of stone working products. A critical analysis of these artefacts, incorporating determination of materials, manufacturing techniques, and rock metamorphosis throughout time, would serve in tracing the modalities of interaction between human civilizations and geological resources (Sciuto, 2018). Minerals and stones are also used as medicine in ancient periods (Wasilewski, 2009). The mineralogical composition of rock samples done by using Fourier transforms Infrared Spectroscopy (FT-IR). To obtain both the chemical and mineralogical composition of archaeological materials FT-IR is an e cient tool (Saravanan et al., 2013). X-Ray diffraction (XRD) used to determine the rock sample's chemical compositions that are in crystalline nature. In the present work, the main objectives are to (i) identify the major and minor minerals present in the rock samples by FT-IR technique (ii) nd the crystallinity index of the quartz and (ii) con rm the minerals by XRD technique.

Geology Of Study Area
Attirampakkam (13.2322°N and 79.8801°E) is an open-air Paleolithic archaeological site located on the southeastern coast of India on 1 km to the north of the tributary of kortallaiyar in Tamil Nadu, (Fig: 1). The village where the oldest known stone tools found in India became the site of a type of Madras culture. The rst well-shaped oval type stone tool was identi ed by Robert Bruce Foote and his colleague William King when they investigated the on 28th September 1863 near sriperumbudur shale beds around to the Attirampakkam (Foote, 1865). It is the oldest Paleolithic Archaeological site in India is dated back to 1.7 million years. But any fossils remains of hominid groups is haven't found on this site. Many archaeological sites in India hominines group fossil remains are found such as Hothnora, Bhimbetka, Adamgarh and Tikoda in Madhya Pradesh as well as Kuliana in Odisha. But more than all of these excavation sites Attirampakkam is one of the oldest Acheulian site in India which was compared to earliest prehistoric antiquity such as, Africa, China, and Europe (Chauhan, 2009).
The sampling site Attirampakkam is located in the kortallaiyar river basin, Tamilnadu, is well known as a lower and middle Paleolithic site in India (Foote, 1865). In 1863 this site was discovered by British geologist Robert Bruce Foote (Pappu, 2001). A comprehensive investigation of this site was continued for over a century. Excavations are well preserved primarily revealing a multicultural base with lower, middle and upper Paleolithic deposits circumstances (Pappu, 2003).

Rock sample collection
With this site 10 rock specimens of different shapes and structures have been collected and packed in polythene bags. These samples were named as AR-1, AR-2, AR-3, AR-4, AR-5, AR-6, AR-7, AR-8, AR-9 and AR-10. The sampling area was located in the tributary stream of the Kortallaiyar river basin (Pappu, 2007). The atmospheric layer of each sample was cleaned and then removed in the laboratory. The remaining sample was crushed for this investigation of this study. Agate motor was used to grain the sample, and these grain powders were sieved using a 63μm mesh screen, and all the particles were the same size. To remove the moisture content of grained powder samples were dried by using hot air oven at 110°C.

Sample Preparation for FT-IR
In this trial, KBr compressed-pellet techniques were used to prepare a sample for the FT-IR technique. In this preparation, 2 mg of powder rock sample was mixed with the 40 mg of KBr in a 1:20 ratio using mortar and pestle (Ramasamy et at., 2005). Before this process the potassium bromide was well grained and dried at 120°C in hot air oven. Laboratory hydraulic press was used to create the pressure in the sample and KBr powder mixer for making pellets. Similar procedure were done by all samples for this technique. Before being put within an appropriate sample holder and applied for the measurement of the infrared beams, the created pellets were kept in a moisture-free container.

Sample Preparation for XRD
A tiny fragment of material weighing about 0.2g was ground manually using an agate mortar for X-ray diffraction investigation.
These powdered samples are stored in plastic vials. Each samples are packaged in a homogenous process for this investigation.
In the study the samples are subjected to the sample holder of the X-ray diffractometer.

FT-IR analysis
The qualitative determination of major and minor minerals in the samples was done by using FT-IR techniques. The identi cation of minerals in rock samples is one of the most valuable and essential applications of infrared spectroscopy investigations (Mullainathan and Nithiyanantham, 2016). Each sample pellets prepared by the same procedure and the spectra were recorded in the mid-range 4000 cm -1 to 400 cm -1 . To the analysis of minerals, infrared spectrum in the range 4000 cm -1 to 400 cm -1 is important (Ikhane, 2020;White and Roth, 1996;Karr, 2013). By comparing pure as well as synthetic mineral values in the literature, the minerals are described based on band position or peak locations. The sharpness or diffuseness of bands, in order to band orientations, may contribute to mineral component identi cation.

XRD analysis
The XRD analysis was used for the structure analysis of the samples such as identi cation of phases, accuracy in unit cell determination, and measurement of particle size analysis. XRD technique is quick and accurate method to identifying the crystal structure and mineral phases (Mullainathan and Nithiyanantham, 2013). X-ray diffractometer has three component such as an Xray tube, a sample holder, and an x-ray detector (Connolly, 2007). The powdered sample was homogeneously spread over an aluminum holder that acted as a sample container in the X-ray diffractometer. The XRD powder pattern of each samples were recorded at ambient temperature. X-ray diffraction peaks are formed by the creative interference of a monochromatic beam of Xrays scattering with speci c angles from each lattice planes of the sample (Bunaciu, 2015). Figure 1 shows the infrared spectra of the rock samples in the frequency range 400-4000 cm -1 . The minerals such as quartz, orthoclase feldspar, microcline feldspar, calcite, kaolinite, montmorillonite, calcite, aragonite and Palygroskite are identi ed in rock samples and its wavenumbers are given in Table 1. In all the investigated samples, quartz, calcite and kaolinite are major minerals and others are minor minerals.

Quartz
Crystallinity nature is con rmed form the observed peak at 695 cm -1 for quartz. If the intensity of this peak increases, the crystallinity increases (Mullainathan and Nithiyanantham et al., 2016;Ramasamy et al., 2003). Quartz is the main silicate mineral and identi ed in all the rock samples. This quartz identi ed at peak 695 cm -1 due to Si-O symmetrical bending vibrations and 778 cm -1 due to Si-O symmetrical stretching vibrations. In addition to that, quartz found at peak 460 cm -1 Si-O asymmetrical bending vibrations. Some other peaks also found at 1615 cm -1 , 1870 cm -1 for quartz due to weathered from metamorphic origin (Ramasamy et al 2009).

Feldspar
Feldspar is a one of the most abundant mineral group on Earth. This mineral group includes the orthoclase, microcline and plagioclase feldspars. In the present work, rock samples of AR8, AR9 and AR10 shows that presence of orthoclase feldspar at  (1987), if four peaks are observed in the region 3697-3620cm -1 , the mineral is said to be ordered state. For collected rock samples, the four peaks are observed at 3625, 3650, 3665 and 3695 cm -1 which indicates that mineral is in ordered state. The clay mineral montmorillonite was identi ed at peaks 479, 1645 and 3440 cm-1 from only samples AR1-AR7. The peak 479 cm-1 appears due to AL-O-Si deformation and peak 1645 cm-1 is due to OH deformation of water. Including with these peaks, strong band 3440cm-1 also observed for montmorillonite due to H-O-H stretching of structural hydroxyl groups and water (Maina et al., 2015). Palygorskite are hydrous Mg silicate clay minerals with brous-like morphologies that typically occur as ne-grained, poorly crystalline masses. In the present study, this mineral was identi ed in the samples AR3-AR7 at peak 515 cm-1 due to Mg (2) octahedral deformation (McKeown et al., 2002).

Carbonate minerals
Carbonate is a key component in uencing both chemical and physical properties of samples; it has been accurately estimated by using FTIR spectroscopy (Tinti et al., Bruckman, et al., 2013Grinard, et al., 2012). Using obtained FT-IR spectrum, carbonate minerals dolomite and aragonite are identi ed by peaks at 1445 and 1085 cm -1 respectively. It seems that dolomite peaks appear at shorter wavelengths of spectrum and invariably present in all the samples due to a strong band between 1430 and 1500 cm -1 due to the CO 3 2stretching vibration whereas mineral aragonite was found only AR3-AR7.

Crystallinity index of Quartz:
In the present stud, quartz is the major mineral present in all the rock samples, hence the crystallinity index of quartz has been calculated. On the other side, crystallinity of quartz will give a clear indication on the crystalline forms of other minerals because quartz is the mineral, which crystallizes last (Ramasamy and Suresh, 2009). Crystalline samples (natural and synthetic) quartz have the highest values of the index of crystallinity. Minimal variation in crystallinity index shows the sustained processes of crystallization and formation of a committed and well-ordered crystal. A spectrum of x-ray diffraction also re ects the presence of crystallinity . The crystallinity index is calculated using the formula Where I 778 is the intensity of absorption band around 778cm -1 due to the vibrations in tetrahedral site symmetry and I 695 is the intensity of the absorption band around 695cm -1 due to the vibrations in octahedral site symmetry. The calculated crystallinity index of quartz is given in Table 3.

X-ray diffraction analysis
The recorded XRD spectra of rock samples are shown in Fig 4. The derived peaks and corresponding minerals are given in table 2.

Conclusion
Using FT-IR and XRD techniques, the 10 archeological rock samples of Attirampakkam were analyzed and their mineral composition were identi ed. The minerals such as quartz, orthoclase feldspar, microcline feldspar, calcite, kaolinite, montmorillonite, calcite, aragonite and Palygroskite are identi ed in rock samples. From the results, it is inferred that quartz, kaolinite, calcite, dolomite, aragonite in crystalline form and others are non-crystalline form which is also con rmed by XRD technique. However, disordered nature of crystal found in rock samples using crystallinity index of quartz.   XRD spectrum of rock samples of Archelogical site of Attripakkam, Tamil Nadu, India