Throughout Servia, Bosnia, Hlum, the Zeta, and Bulgaria there were thus numerous Ragusan colonies. As a rule mining was the chief industry, and it was in the mining districts that the commercial settlements were to be found. In Roman times the mines of Illyria were well known; they were abandoned at the time of the barbarian inroads, and it was not until the twelfth and thirteenth centuries, at the time of the rise of the Serb States, that the industry revived. Wonderful tales were told by mediæval travellers of the richness of the Balkan mines. As late as 1453 the Greek Critobulus asserted that gold and silver sprang from the earth like water, and that wherever you dug you found large deposits of the precious metals, in greater quantities than in the Indies.[246] King Stephen Uroš II. Milutin (1282-1320) was the first to summon in German miners, called Sasi (_i.e._ Saxons), so as to benefit by their superior skill, but the Ragusans were also numerous. Many of the technical terms relating to mining still used in Bosnia are of German origin: _orat_ = _Ort_; _hutman_ = _Hüttenmann_; _karan_ = _Karren_. The ore was extracted from galleries and shafts, many of which are still in existence. The refining of the metal was executed at Ragusa or Venice. Gold, silver, lead, and iron were the chief products of the Bosnian and Servian mines. Gold, of which the earliest mention is in 1253, was found chiefly in the neighbourhood of Novobrdo (Novus Mons, Nouomonte, Νοβοπύργον), which was for a long time the largest city in the interior of the Balkan peninsula between the plain of Kossovo and the Bulgarian Morava, three miles east of Priština. Silver, however, was found in much larger quantities. Of this metal two kinds are mentioned in the Ragusan annals, _i.e._ _argento bianco_ (white silver) and _argento de glama_ (_glamsko srebro_ in Slavonic), which had a slight gold alloy. Srebrnica was the chief centre for the silver-mining industry. Lead was another important product, and was in much request for the roofing of houses and churches. Sometimes a whole caravan of 300 horses journeyed from the mining districts to Ragusa laden with nothing but lead. The iron output gave rise to various active industries, both locally and at Ragusa, where Bosnian iron-workers were often employed by the Republic. A certain amount of copper was also found, and there were tin and quicksilver mines in the Kreševo district. The principal mining centres thus were: Kreševo and Fojnica;[247] Srebrenica, near the Drina, chiefly for silver;[248] Zvornik on the Drina, for lead;[249] Rudnik, where there are traces of Roman mines mentioned by Ragusan documents of the thirteenth century; Kopaonik, for silver and iron;[250] Novobrdo, for gold and other metals;[251] Kučevo and Brskovo, which flourished at the end of the thirteenth century.[252]