Metals and metal working had been known to the people of modern Italy since the Bronze Age.  By 53 BC, Rome had expanded to control an immense expanse of the Mediterranean. This included Italy and its islands, Spain, Macedonia, Africa, Asia Minor, Syria and Greece; by the end of the Emperor Trajan's reign, the Roman Empire had grown further to encompass parts of Britain, Egypt, all of modern Germany west of the Rhine, Dacia, Noricum, Judea, Armenia, Illyria, and Thrace (Shepard 1993). As the empire grew, so did its need for metals.
Central Italy itself was not rich in metal ores, leading to necessary trade networks in order to meet the demand for metal.  Early Italians had some access to metals in the northern regions of the peninsula in Tuscany and Cisalpine Gaul, as well as the islands Elba and Sardinia.  With the conquest of Etruria in 275 BC and the subsequent acquisitions due to the Punic Wars, Rome had the ability to stretch further into Transalpine Gaul and Iberia, both areas rich in minerals.  At the height of the Empire, Rome exploited mineral resources from Tingitana in north western Africa to Egypt, Arabia to North Armenia, Galatia to Germania, and Britannia to Iberia, encompassing all of the Mediterranean coast. Britannia, Iberia, Dacia, and Noricum were of special significance, as they were very rich in deposits and became major sites of resource exploitation (Shepard, 1993).
There is evidence that after the middle years of the Empire there was a sudden and steep decline in 
mineral extraction.  This was mirrored in other trades and industries.
One of the most important Roman sources of information is the Naturalis Historia of Pliny the Elder.  Several books (XXXIII–XXXVII) of his encyclopedia cover metals and metal ores, their occurrence, importance and development.