Abstract
The discovery of three outstanding Achaemenid buildings in Borazdjan Plain territory, such as “Charkhab”, “Sang-Siyah” and “Bardak-Siyah”, unveiled a new domain in the archaeological study of the Persian Gulf hinterlands and in the Achaemenid era. Excavation in the surrounding areas of these three buildings in two courses in the years of the decades 1350s and 1380s, led to the expsition of their different parts and architectural details. The presence of remarkable Achaemenid architectural elements including the central columned hall, lateral pillared porches and stone column pedestals, as well as the locality situations of the palaces on the plain and peripheral areas of the permanent “Dalaki” and “Shapur” and the seasonal “Ardu”rivers, made new theories possible about the quality and the reason of choosing the location and the erection of a government edifice in the Achaemenid era, while putting forward some general questions about the spatial structure of each palace. Because of the roughcast excavations, our information about the spatial extent of the unearthed collections is quite incomplete. In “Charkhab” site, for being in the vicinity of the seasonal “Ardu” river, there has been more than 1.5 meters of sedimentation which makes it difficult to access Achaemenid findings. So we decided to use new archaeological methods especially archeo-geophysical survey to study around the site and then continue the excavation around the palace according to the results obtained. So, in the first step, the western and north-western fronts with the extent of 13 hectares were surveyed archeo-geophysically using a magnetometric method and according to the outputs and the final produced map and the scatteration of exposed anomalies, some locations were determined for trenches and excavation. According to the maps obtained through magnetometry, some trenches were selected in zones where the abundance of anomalies was evident. In total, two trenches CH II and CH III, each with the dimension of 10×10 were excavated, while most findings were obtained from an Achaemenid leyer in trench CH III in the depth of 153 cm, where items such as baked bricks with the dimension 32×32×8 with bitumen mortar similar to those of Charkhab Palace, gate-pivot stones and pillar foundations worked with raw stone, pieces of cream colored pedestal stones and the most important of all, pieces of cornoture with horizontal strings similar to that of “Bardak-Siyah” Palace and  the specific palace of Cyrus at Pasargadae, can be mentioned
Keywords: Borazjan, Charkhab Palace, Archaeogeophysical Survey, Magnetometry, Excavation of Charkhab Site.

Introduction
Describing the importance of the Persian Gulf and its geopolitical role in the Achaemenid period, Herodotus describes the actions of “Scyllax Cariandi” and the order of Darius II to identify a sea route from the Indus River in India to Egypt, which was used by Indians and Iranians (Herodoutus, 1828: 289). 
In addition, other well-known historians and geographers of the early Christian centuries, such as Strabo, Arian, and Ptolemy, mentioned the Persian Gulf with titles such as “Persicon Kitas” and “Sinus Persicus”. 
The commercial prosperity of its shores is described in interaction with the West and the East. (Bayat, 1988: 28). 
Generally speaking, it can be inferred that the northern shores of the Persian Gulf inspecial, were of great importance during the Achaemenid period and later, and the construction of magnificent architectural works and government landmarks have not been unexpected.
The discovery of the remains of three outstanding Achaemenid landmarks in Borazjan plain titled “Charkhab”, “Sang-e Siah” and “Bardak-Siah”, opened a new chapter in the archaeological studies of the Persian Gulf and the Achaemenid history as well.
Excavation of these buildings during two seasons in the 1350s and 1380s, led to the discovery of various sections and their architectural components. 
Considering the presence of prominent elements of Achaemenid architecture, including the central columned hall, the side columned porches and stone pillars, along with the location of these palaces in the plains and the banks of Dalki and Shapur rivers and the seasonal Ardo valley, it has been tried to provide a definitive answer to existing questions and hypotheses based on current studies in this article. 
Asking general questions about the spatial structure of each of these palaces, provided new insights into how and why to choose a location and build a government building during the Achaemenid period. 
An important question in this field is whether these palaces were only used as summer accommodation facilities or they have been used as government seats.
Hypotheses in this study, basically suggest that the development of maritime trade, offshore communication routes, as well as suitable environmental structures and facilities, have led to the Achaemenid settlements in Borazjan plain. 
Achaemenid palaces discovered in Borazjan plain are part of the urban structures in that period. Some Achaemenid relics discovered, such as the Charkhab Palace, might have been left incomplete due to improper site selection and unsuitable location.
Architectural structures and spatial analyzes of the sites discovered in the Borazjan plain, are probably modeled on the architecture of the earlier Achaemenid culture in Pasargadae.
Studies of the surroundings of these sites show that there are other spaces related to the palaces. Based on geophysical studies as well as archaeological surveys around the sites, it can be imagined that these palaces were a collection. Further information on this subject, needs further archeological excavations and research.
One of the most important Achaemenid buildings on the northern hinterlands of the Persian Gulf is Charkhab Palace, which was accidentally discovered in 1350, during the bulldozing operations of water transfer pipeline from Borazjan to Bushehr, through the date palm groves on the western suburb outskirts of Borazjan and in the so-called “Charkhab area”.  
After preliminary investigations and the similarity of the discovered structure with the stone columns used in Pasargadae, it was decided to explore the place of discovery. The result of this excavation led to the appearance of different parts of the remains of a magnificent Achaemenid building (Sarfaraz, 1350 and 1351; Ebrahimi, 1391). Simultaneously with the excavation of Charkhab site and following the public reports that similar relics were found close a nearby village called Jatut / Jatal; Sarfaraz was able to discover another building on the banks of Dalaki River called Sang-e Siyah, about nine kilometers north of Charkhab. 
This site was excavated in 1977 by Ismail (Ehsan) Yaghmaei (Yaghmaei, 2005: 9-11; 2018: 191-196; Ebrahimi, 2012). 
During the exploration of the Sang-e Siyah remains and in the surrounding areas and palm groves, the excavations led to the discovery of another building called “Bardak Siyah” which means “the black stone”, among the palm groves of Dorudgah village. 
Yaghmaei explored the building and continued his excavations during the winter and the spring of 1978 (Yaghmaei, 2005; 1397; Ebrahimi, 2012). 
In the 2001s, with the resumption of archeological activities in Bushehr province, the Charkhab building, which had been buried under the flood deposits after the first exploration period, was excavated again by Sarfaraz in five consecutive seasons. 
In addition to the sections that were appeared earlier, some other new parts of the building became visible again. (Sarfaraz, 2001; 2003; 2004; 2005; 2006).
Due to unfinished excavations, our knowledge of the spatial extent of these collections is very limited. 
In the Charkhab area, the settled sediments are more than 1.5 meters high, due to its proximity to the Ardo seasonal river. This has made it difficult to obtain necessary findings from the Achaemenid period.
The study of archeogeophysics today, plays a crucial role in identifying the points and structures of ancient layers.
Using this methodology, saves time and also achieves the desired results much faster, much easier and much more accurately.
Therefore, we decided to use these new archeological methods, especially archaeogeophysical surveys, to conduct research around this area, and based on the results of these studies, to continue exploring around the palace.
Therefore, in the first place, the western and northwestern fronts of the palace, with an area of 13 hectares, were examined by magnetometric archeogeophysics, which revealed the dispersion of anomalies according to the output and finalized maps, and places for trenches and excavations were determined.
According to magnetic output maps, trenches were selected in areas where the abundance of anomalies was apparent.
Totally, two trenches ChII and ChIII with dimensions of 10 x 10 were excavated and most findings were obtained in trench ChIII at a depth of 153 cm and in an Achaemenid layer. 
In the cultural findings of the recent excavation in Charkhab, paddy parts of the columns with cream-colored strings are important.
Examples found in Bardak Siyah and Sang-e Siyah, are also comparable to the example of the private palace of Cyrus the Great in Pasargadae.
These paddy parts are quite different from the paddy parts obtained in Charkhab Palace (ChI), which are round and black without any carvings.
It seems that this collection (ChIII) is similar in architectural elements to those of Bardak Siyah and Sang-e Siyah palaces and those of the private palace of Cyrus the Great in Pasargadae.
The cream-colored base stone of the gateway as well as the foundations of the columns found in the ChIII trench are similar to those of Charkhab(ChI) and Bardak Siyah palaces.
The bricks obtained with  the dimensions of 33 x 33 x 8 cm and bitumen mortar in this trench are comparable to those found in the palaces discovered in Borazjan.
Given the architectural elements obtained, it is possible that this complex had been built earlier than the Charkhab Palace (ChI) itself.
Undoubtedly, more studies and more extensive research are needed to answer all the hypotheses and questions.

Abstract
Due to the extent of the empire’s territory, the remains of the Achaemenid stone pillars have been registered in different parts of Iran. The remains of this architectural style can be seen in the monumental set of Pasargadae, Persepolis., Naqsh-e Rostam, Lidoma and Tomb-e Bot in Fars Province, the remains of Shush in Khuzestan Province, and stone works of Ecbatana in Hamedan, Rivi Palace in Northern Khorasan Province, and Achaemenid palaces in Borazjan region in Bushehr province. The rock mining of these monuments was recognized as local. However, in Boushehr Province, two ancient mines of Pouzepalangi Rahdar and Tang-e Gir of Borazjan Region have been named. The maximum extraction and application of the crème color stones from the Puze- Palangi mine were registered from the palaces of the Borazjan Region. However, for the geological structure of the black-gray stone of Acamenian palace in Charkhab of Borazjan, samples of this type of stone were extracted from Charkhab palace. These samples were compared with the gray-black samples of the Bardak-e Siah and Sang-e Siah Palaces of Borazjan. With the petrographic studies of thin sections obtained from the palaces and chemical analysis of XRD and XRF, the structural process of the gray-black samples of the Achaemenid palaces of the Borazjan region entered a new stage. The results of the petrography studies indicate that the gray-black stone samples of Charkhab palace corresponded to the sample of Sang-e Siah Palace and Badak-e Siah, considering the microsprite and sprite background, and the few amount micrite as well as the layered structure. Also, the analysis of the analytical samples of XRD and CRF of these stones indicates that the samples of Charkhab Palance and Sang-e Siah are the same. Given that no trace was found in the mining for the gray-black stones in Boushehr Province so far, it can be then claimed that these stones were extracted from a non-local mine. 
Keywords: Borazjan, Charkhab Palace, Bardak-e Siah Palace, Sang-e Siah Palace, Petrography, XRD, XRF.

Introduction
The coasts of the Persian Gulf, especially the ports of Bushehr and Borazjan in the golden age of Elam, i.e., the late 2nd millennium BC, has been one of the important centers of trade and the interface between the sea route of Shush and India. The fertile and tropical areas of Dashtestan were among the areas where the Achaemenid dominated shores and benefited from the proximity to the sea. They provided places for themselves in these areas so that they could spend the winter there. The building of Charkhab Palace in Borazjan is known as the winter palace of Achaemenid Cyrus due to its great similarity with the private palace of Cyrus in Pasargadae.
Research Questions and Hypotheses: The main questions of research are as follows: What is the structure of black-gray stones used in the Achaemenid architecture of Borazjan palaces? What is the structural relationship between black-gray stone in the Achaemenid palaces of Borazjan (Charkhab, Bardak-e Siah and Sang-e Siah)? Based on current studies, what opinion can be expressed about the mines of Borazjan Achaemenid palaces?
Research Method: Petrography and analytical methods of XRF and XRF were used to the geological structure of the gray-black stones of the stone pillars of Charkhab Palace in Borazjan. In the meantime, using the research method thin-walled structure to observe the minerals and adopting the samples were done with the OLYMPUS BX51 polarizing light transmission microscope, made in Japan, with the capability of filtering light in the XPL mode of the analyzer and emitting polarized light. XRD experiments to identify and detect the crystalline phases forming in the study samples and qualitative and semi-quantitative determination of crystals by powder method (with Cu) target radiation lamp with a maximum potential difference of 40 KV and maximum current intensity of 30 mA, fixed sample and Needle detector) was performed on three samples of historical palace stones in Bim Gostar Taban laboratory in Tehran. The results were analyzed by High Score Plus software. XRF experiments were performed to identify and quantify the constituent elements of study samples of Achaemenid palaces by powder method and with the model device: PW1410 Manufactured by PHILIPS Netherlands in Bim Gostar Taban laboratory in Tehran on the same three samples.

Research Background 
Borazjan city is located 67 km from Bushehr and 226 km from Shiraz. Due to the discovery of a piece of a stone pillar base when digging a water canal in Borazjan in 9171, the General Directorate of Archaeological Research of Iran assigned Dr. Ali Akbar Sarfaraz to explore the site in which this work was discovered.  Dr.Ali Akbar Sarafraz was the head of the Iranian Archaeological Board in Bishapour at that time. Therefore, archeological operations began in this ancient area, and at the end of the one season of the excavation, the main form and structure of the columned hall were manifested. In a study entitled “Spatial analysis of the Achaemenid palaces in Borazjan” the appearance, location, and objects obtained from these sites have been discussed.

Petrography Results 
The gray-black stone of all three Achaemenid palaces of Charkhab (CH1, CH2, and CH3), Bardak-e Siah (BS1), and Sang-e Siag of Borazjan (SS1) are calcareous and boiled in contact with 0.1 normal hydrochloric acids. These carbonate rocks have a microsparite texture to sparite, and are micrite to a small amount, and have few quartz grains.

XRD Analysis of Gray-Black Stone Samples of Achaemenid Palaces in Borazjan Region 
The spectrum of gray-black stones of the Achaemenid palaces of the Borazjan region, which includes the samples of Charkhab Borazjan (CH3), Bardak-e-Siah (BS1), and Sang-e-Siah (SS1), the matching of the spectra of the same limestone is observed. However, based on the peak intensity of calcite in the samples of Charkhab Palace (CH3) and Sang-e Siah (SS1), which shows 11000, are placed in one group. Also, the sample (BS1) with a peak intensity of calcite over 14000 is observed separated from the group.

XRF Analysis 
In the analysis of the black-grey stones of the Achaemenid palaces, the sample of grey-black stones of palaces has been compared as only the samples of palaces are available. Also, the possible mine of the black-grey stones has not been reported in Boushher Province so far. Accordingly, the oxide of the main elements, such as SiO2, CaO, P2O5, TiO2, and MgO, represents particular values in the table. These values are approximately close to each other in the sample of the grey-black stones of the Achaemenid palaces. Therefore, they are considered an appropriate indicator of similarity. Graphs of oxide values of SiO2, P2O5, TiO2, CaO, and MgO of the samples are consistent. Also, the accordance of the oxide values of the mentioned elements, the values of the secondary elements (in terms of ppm) of the gray-black stones of Charkhab (CH3), Bardak-e Siah (BS1), and Sang-e Siah (SS1) rocks are observed.

Analysis and Discussion  
Using the laboratory and scientific methods and comparing the results of this paper with the results of the papers on Pasargadae and Persepolis, the relationship between the sources of extraction of gray-black stones of the complex of Achaemenid monuments in Borazjan Region of the Fars province mines, Majdabad mountain mine in particular, around the Perspolis and Sarpaniran and Ahmadbegi Mines in Pasargadae is rejected. The presence of several large pieces carved from this type of stone in the east of the Achaemenid palace of Charkhab Borazjan confirms that Charkhab palace was in the process of construction. However, these stones which have been left on the ground two hundred meters east of the palace, are reasons for the existence of a stone-cutting workshop of Charkhab palace or another building that has not been excavated yet.

Conclusion 
Studies on the gray-black rocks of Achaemenid palaces show that mining traces or mine exposure of this kind of stone have not been seen or reported in the region. Therefore, it seems that these mines were not local, and the stones were supplied from other sources. Also, the hypothesis based on that the grey-black stone mines might have been local depends on the more extensive field studies in the future.