Microstructural Investigation of Some Bronze Artifacts Discovered in a Dacian Site Using Non-Destructive Methods

Abstract

Dacian civilization flourished on the actual territory of Romania during the Late Iron Age and had its peak from the first century BC to the first century AD. They had intensive relations with Hellenistic and Roman civilizations. Therefore, it is difficult to evaluate the origin of some widely spread artifacts discovered in the Dacian archeological sites. The present research is focused on two bronze artifacts (a bronze coin and a mirror fragment) found in the Alun-Piatra Rosie site and a silver coin found in the Ardeu site. Artifacts were investigated with nondestructive methods such as SEM-EDX for microstructural and elemental characterization, and the crystalline phases were investigated using XRD. Bronze coin proves to be an Istrian issue having an elemental composition of 75.0% Cu, 20.8% Sn, and 4.1% Pb, which corresponds to a structure of Cu grains mixed with Cu5.6Sn grains. The bronze mirror fragment has an elemental composition of 52.3% Cu and 47.7% Sn, which corresponds to a structure containing grains of Cu6Sn5 mixed with grains of Cu41Sn11. It has a smooth surface that was investigated with AFM microscopy, which evidences a Ra roughness of 51 nm for the patina surface and 33.7 nm for the clean metal surface, proving the high quality of the original mirror luster of the artifact. The silver coin was identified as a Radulesti–Hunedoara type meaning that it was produced in local Dacian metallurgic workshops. It has an elemental composition of 63.1% Ag, 25.3% Sn, 7.8% Cu, and small traces of P and Fe, which corresponds to a structure of Ag grains and Ag3Sn grains. Silver coins show that Dacians uses Sn as alloying element in their metallurgic workshops. Istrian bronze coin proves to be typical for Hellenistic or Roman bronze type with Sn content no more than 25% Sn. The bronze mirror fragment has an unusual composition that might be a result of al local metal charge elaboration with several Hellenistic and Roman bronze pieces as raw material and an extra Sn addition during the melting process. This material facilitates the polishing properties of the active surface that has a very low roughness even after 2000 years of ground resting and adherent oxides patina.

Ag and Sn Implications in 3-Polker Coins Forgeries Evidenced by Nondestructive Methods

“…It indicates that the molten bath contains a tinrich bronze instead of pure tin [37,38]. It facilitates the formation of a small adhesion interlayer to the copper blank, which assures a more resistant coating, a fact reported in the literature for high-tin bronze artifacts [39,40]. Statistical analysis clearly shows that these forgeries are a distinct group.…”

Microstructural Investigations Regarding Sustainable Recycling of Ceramic Slurry Collected from Industrial Waste Waters

“…Each mineral has its own color range depending on its position relative to the microscope optical axe. Therefore, quartz exhibits green-gray shades, kaolinite has a pale blue-bright white nuance, mullite presents reddish brown to reddish pink shades and lepidocrocite's nuances vary from the dark brown to intense red [33,34]. The composition is dominated by quartz, followed by kaolinite and mullite.…”

Effect of Alloying Additives and Moulding Technology on Microstructure, Tightness, and Mechanical Properties of CuSn10 Bronze

“…Tin bronzes belong to the group of copper alloys, which have the longest history [1][2][3]. Their functional properties were discovered in prehistoric times, giving a name to an entire era-the Bronze Age [4,5]. Due to their excellent mechanical properties resulting from the addition of tin to copper, tin bronzes were used for the production of tools and weapons, among other applications [6,7].…”