A team of archaeologists led by Im Sok Rithy, deputy director of the Apsara Authority, and Dr Ea Darith, has confirmed the discovery of an ancient iron-smelting works within the grounds of the Angkor Archaeological Park following excavations carried out in March.

The discovery is the first of its kind so near the seat of power of the Khmer Empire and, for Im, shows the value of good old-fashioned archaeological methods. 

“For 150 years, this site has escaped the attention of local and international researchers, and hadn’t been detected by any aerial photograph or even LiDAR.”

LiDAR, a ground survey method using lasers, in 2012 revealed, among other things, the scale and complexity of Mahendraparvata, the Khmer Empire’s foundation city on Phnom Kulen.

Instead, the discovery came about following a seminar held by the Apsara Authority in November 2015 on the use of iron slag (a byproduct of iron smelting) for treating skin conditions.

One of the local commune chiefs who had been invited to attend surprised officials when he informed them that there remained some iron slag in the rice fields in his commune. And so the process of surveying and digging began. 

Until now, researchers believed that iron used in Angkor came from sites far from the complex. Iron ore smelting is an intensive process that requires a lot of fuel.

In the capital’s population-heavy environs — at one point the largest metropolitan area in the world with a population of up to one million people — wood would have been relatively scarce. 

“This is the first such discovery in the heart of Angkor,” said Im. “We may need to rethink all the old assumptions about all the metal used in Angkor coming from Preah Khan Kampong Svay in Kampong Thom, Phnom Dek in Preah Vihear, and Buriram in Thailand.” 

The discovery has highlighted the limitations of some high-tech archaeological techniques. Photo supplied

Excavations of the site 2 kilometres north of Phnom Bok carried out in March revealed iron slag, tuyere (bellows pipes), iron ore, ceramics and a furnace. Im reckons the site may have been missed as rice farmers disturbed and distributed the usual giveaway sign of mounds of iron slag, of which several tonnes can be produced by any one site. 

Mitch Hendrickson, an assistant professor at the University of Illinois at Chicago and one of the world’s foremost authorities on Angkor period metal working, was happy to hear about the remarkable discovery. 

“This is an important find that needs to be studied in detail to determine how much material was produced and, more importantly, when the site was active,” he said.  

Im suggested that based on analyses of the ceramics found at the site, it most probably operated during the Angkor period. However, samples of materials have been sent abroad for radiocarbon analysis that will provide more information. 

Iron played an important role both in sustaining and expanding the Khmer Empire. “It was very important, but in a ‘silent’ way,” said Hendrickson. “The texts do not really discuss it, but iron would have played a key role in agriculture, warfare and building.” 

Without it, the intricate carvings that grace the walls of Bayon and Angkor Wat, and so many others, could not have been realised. The temples themselves would not have been built. Iron also played a part in maintaining the water management system on which the empire depended so heavily.”

According to Hendrickson, iron first appeared in Cambodia around the 5th century BC, most likely via India or China. According to current understanding, there is no evidence of a Khmer smelting tradition, but the ethnic minority Kuay, based around Phnom Dek in Preah Vihear, have a tradition that dates back to the 16th century. 

“This does not mean that the Kuay were the only ones,” he said. “They are just the only ones that we know smelted at that time.

“The technique is difficult and the secrets of smelting are often kept from others.”