Chemical Compositional Signatures of Constituent Minerals of Iron Slags and Ores from the Khmer Monuments

Abstract

Iron slags and ores were collected from 22 sites (A to V) in Preah Khan of Kompong Svay, the area surrounding Phnom Daek, and the Angkor monuments. Iron ores were taken from two outcrops in Phnom Daek. The chemical compositions of fayalite and wüstite in the iron slags and magnetite in the iron ores were determined using a scanning electron microscope equipped with an energy dispersive spectrometer. Cluster analysis and principal component analysis using averaged chemical compositional data for fayalite allowed for the investigated slag dumps to be classified into two main groups: Groups 1 and 2. The slag dumps in the area surrounding Phnom Daek and those in the Angkor monuments were classified as Group 1, and those in Preah Khan of Kompong Svay were classified as Group 2, except for sites C and U, which were classified as Group 1. Radiocarbon dating was carried out on 10 charcoal fragments from slag dumps outside the Angkor area. The dating results indicate that iron making in Preah Khan of Kompong Svay was conducted in and after the 13th century except for sites C and U, where iron ores may have been supplied from Phnom Daek before the 13th century.

Luminescence dating of archaeometallurgical slag from Buriram Province, northeastern Thailand

“…Whereas, for heap 1, the OSL date of 140 ± 10 y ago makes it the youngest iron smelting industry in Ban Kruat, if not northeast Thailand. Indeed, this date for heap 1 conformed well with the radiocarbon dates (140 ± 20 y BP) of a slag site in the Angkorian lowland (Cambodia) [33], suggesting that iron smelting in Ban Kruat might have taken place during the late 19th century; although, it is unsettled if the activity was continued from the Angkorian period.…”

“…The results of slag dating from two slag heaps suggested three different periods of iron-smelting production: early 14th (BK 2-4), mid 16th (BK 2-3) and late 19th centuries (BK 1-1) as shown in Table 2. This chronological difference is also observed in the studies by Hendrickson et al [32] and Uchida et al [33] using AMS dating of in-slagcharcoal which illustrated slag heaps at Preah Khan of Kompong Svay lasted in later periods of activities.…”

Remote sensing and luminescence dating of archaeological sites in Buriram province, northeastern Thailand

“…Whereas, for heap 1, the OSL date of 140 ± 10 years ago makes it the youngest iron smelting industry in Ban Kruat District, if not Northeast Thailand. Indeed, this date for heap 1 conformed well with the radiocarbon dates (140 ± 20 years BP) of a slag site in the Angkorian lowland (Cambodia) (Uchida et al, 2019), suggesting that iron smelting in Ban Kruat District might have taken place during the late 19 th century; although, it is unsettled if the activity was continued from the Angkorian period.…”

“…The results of slag dating from two slag heaps suggested three different periods of iron-smelting production: early 14 th (BK 2-4), mid 16 th (BK 2-3) and late 19 th centuries (BK 1-1) as shown in Table 3.2. This chronological difference is also observed in the studies by Hendrickson et al (2013) and Uchida et al (2019) using AMS dating of in-slag-charcoal which illustrated slag heaps at Preah Khan of Kompong Svay lasted in later periods of activities. The most recent date of slag from heap no.1 was the youngest date in the lower Northeast Thailand; therefore, comparing the three dates for the two heaps, it can interpret that the iron-smelting activity at heap 2 (Figure 3.1b) was terminated around 470 ± 7 years ago, whereas, at heap 1, it continued to 140 ± 10 years ago.…”

“…Furthermore, questions concerning the transformation of technologies and production organisation over time are very difficult to address based on current evidence. Looking outside Thailand, few studies have clearly illustrated smelting evidence belonging to historical periods: the 8 th -9 th century AD iron smelting in Saphim, Northwest Lao PDR (Évrard et al, 2016;Pryce et al, 2011) and production during the Angkorian Khmer (Hendrickson et al, 2019;Leroy et al, 2018;Leroy et al, 2015) to post Angkorian Khmer period in Cambodia (Hendrickson et al, 2013;Hendrickson et al, 2017;Hendrickson et al, 2018;Pryce et al, 2014;Uchida et al, 2019). The latter identified the distribution of 18-22 slag deposits/sites with Preah Khan of Kompong Svay, east of Angkor, demonstrating the continuation of iron smelting activities from mid-13 th to the early 17 th centuries with the possibility of pre-13 th century production.…”