Studies of Coins of Medieval Volga Bulgaria by Neutron Diffraction and Tomography

The phase composition and spatial distribution of chemical components in the volume of coins of medieval Volga Bulgaria are studied using the neutron-diffraction- and neutron-tomography methods. Two coins belonging to different time periods of this medieval state are studied: a Samanid multidirham dating from the first half of the 10th Century and a silver dirham dating from the period of the reign of the Bulgarian emir Bulat-Timur. It is established that both coins consist of a copper-silver alloy. In the Samanid multidirham, the average volume contents of copper and silver are found to be about 50%. Minor spatial variations in the chemical composition are found in the volume of the multidirham under study. It is established that the volume average silver content in the Bulat-Timur dirham is about 95%.