**1. Introduction**

#### **1.1. History**

78 The Development and Application of Microwave Heating

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Heating of Mineral and Organic Materials. Rijeka, Croatia: InTech. pp. 697-722

Mineral and Organic Materials. Rijeka, Croatia: InTech. pp. 723-752

The thermal treatment of ore to bring about thermal fracturing, and thereby a reduction in Ore strength is by no means a novel idea. The first century BC Greek historian, Diodorus Siculus, recorded in his Bibliotheca Historica the ancient practice of fire setting, verifying his work with that of another Greek historian, Agatharcides, who had visited the gold mines in Egypt around the second century BC (Meyer, 19971).

Oldfather, 19672, provides a translation of Diodorus's account of the practice: "The gold bearing earth which is hardest they first burn with a hot fire, and when they have crumbled it...they continue the working of it by hand; and the soft rock which can yield to moderate effort is crushed with a sledge".

The practice of fire setting basically consisted of constructing a large fire against the rock face to be mined. As the rock heated unevenly, it would fracture internally, severely weakening the rock. After the fires died down the rock face would be doused with water, though whether this rapid quenching was employed to further weaken the rock or to allow the miners to immediately continue working the rock face is not known (The Tech, 1886)3.

Using this process, it was possible to weaken the rock face to the depth of approximately a foot at a time, after which the soft ore was mined and when the harder rock face was again encountered, fire setting was again employed (Cowen, 1999)4.

Archeological evidence supports the notion that the practice of fire-setting was a worldwide phenomenon and may indeed be much older than those activities reported in the records of Diodorus Siculus, with ancient mining sites discovered at Rudna Glava in the Balkans suggesting the use of fire setting around 4500 to 4000 BC, at Ai Bunar in southern Bulgaria

also dated at several thousand years BC and from which it is estimated that between 20 000 and 30 000 tonnes of ore were mined while employing the method when required (Cowen, 1999), at the ancient mining sites around Isle Royale in the Lake Superior region in North America to mine copper and up until just a few centuries ago in Japan for creating long tunnels (The Tech, 1886)3.

In fact, it remained a vital part of the mining industry until the first use of gunpowder for blasting in 1613 (The Tech, 1886)3, after which the use of thermal treatment declined in favor of the quicker processes of drilling and blasting.
