A Study of the Technical Features of Gem Engraving Wheels in 13th to 16th Centuries on the basis of Jawāher-Nāmas (Books of Gems)

Gemology is one of the first sciences about which ancient scholars and scientists of Iran and the Islamic world have written treatises. The economic, administrative and documentary aspects of gems in Islamic governments and before them show the importance of this part of science in different periods. The main part of Jawāher-namās (books of gems) has always been dedicated to methods of identifying and valuing gems. But in the meanwhile, the subjects of civilization, medical sciences, hadith sciences and technical aspects of stone engraving and polishing have also been considered. In Jawāher-namās, the methods of cutting and polishing each type of gems has been specifically described. Such descriptions are sometimes accompanied with specialized or forgotten words. Therefore, understanding and discovering the knowledge of our predecessors in this regard has been remained ambiguous and in some cases, the exact meaning of the authors would not be understood. These include a variety of engraving and polishing wheels (instruments). In most gems the types of wheels used have been referred to; however there is no mention of the general structure of them, i.e. the devices used. Therefore, the main question of the present research would be as follows: What characteristics do the engraving wheels mentioned in Persian Jawaher-namas have in terms of meaning, appearance, structure and function? Looking for sources other than books on gems, and reviewing the remained examples and pictures used to describe this work in the 9th and 10th centuries AH/AD 15th and 16th centuries, an attempt has been made to give an overview of the construction of such devices and the function of each. Examining some images and tools left from the Qajar period in Iran, India and Europe, the results demonstrate that these wheels were based on relatively similar structures at that time. However, there are three types of lapidary wheels that require three different types of machines. In this article, besides having a review of such devices, other technical features and the history of each has been considered as well. These features show that each lapidary wheel applied a certain device with different function, depending on their operation. This matter proved to be decisive in the diverse production of gem stones.