Copper From the Bronze Age to the Fall of Rome
Copper From the Bronze Age to the Fall of Rome
Replaced by iron for weapons and tools, copper and bronze became metals used in architecture, art, and certain specialized uses such as copper pots. The alloy brass, in which copper is mixed with zinc, was discovered sometime before 600 B.C.
The state of Lydia, south of Troy in western Turkey, invented
the idea of coins as a medium of exchange. Coins were small and
portable, had a set value, and were more convenient for trade
than the bulky system of barter. Gold, silver, copper, and bronze
were used for coins, a use that continues today in our penny. 
Greek coins with the head of an owl on the back,
known as "Owl Coins", were the most important medium of
exchange in the 5th century B.C. Thus, the idea of money was
born.
The Etruscans reached the glorious days of their civilization about 800 B.C., before the rise of Rome. They were descendents of immigrants from Lydia. In the mountains of the modern Italian province of Tuscany, the ancient Etruscans found copper and tin ores. Iron ore was conceniently near on the Island of Elba. While they created superb iron weapons, they produced magnificent statues in bronze. Joining the Phoenicians in seafaring trade, the Etruscans were rivals of Greek traders around the Mediterranean Sea. Caught between Gaulic invasions from the north and the rising Roman city-state to the south, the last Etruscan city yielded to Rome in 396 B.C.
Rome explored all around the Mediterranean for mineral wealth
to support its growing empire. The Romans also acquired immense
Phoenecian mineral wealth when they destroyed the Phoenecian
colony of Carthage. This wealth included the great metal mines of
Spain. A huge copper deposit was found in the soutwest corner of
Spain. Copper and iron on the surface of the Earth at that
deposit colored a nearby river red. It is thus called Rio
Tinto. The mining district was named Rio Tinto as well.
The deposit originally consisted of a reddish mountain, with
iron, silver and gold as well as copper. 3000 years of mining
have left a crater where the red mountain once stood. 
The crater is over 800 feet deep and over
three-quarters of a mile wide. In the walls, one can see remnants
of Roman tunnels and shafts. Water wheels with bronze axles used
to lift water out of the ancient tunnels are still found. Slaves
ran the water wheels by walking on treadmills.
Mining techniques had changed little. Besides using fires to crack rock, quicklime was stuffed in cracks, then wetted with water. As it became wet, the quicklime expanded, breaking off chunks of rock.
To allow miners to carry ore to the surface, spiral stairways were cut in the rock around the sides of shafts. Where the space was too cramped for stairs, notched poles were used as ladders. Up to 200 hundred pounds were carried by each worker, in leather buckets on their backs.
The deep mine workings tended to fill with water despite the water wheels. A drainage tunnel over a mile long and reaching a thousand feet deep was dug to join up with the mines.
In the early days of the Roman empire, conquests of new lands
were being made at a great rate. As a result, many prisoners of
war were carried to Spain as slaves. Because slaves were
plentiful, conditions were horrible for workers in the mines.
Later in the Roman empire, when new slaves were less easy to
obtain, slaves became more valuable. Roman labor laws were passed
that mandated working conditions for the slaves in the mines.
Tunnels and shafts had to be supported adequately with timbers,
in order to prevent collapse. 
Miners
were entitled to sleeping and bathing accommodations, food, and
specific hours of work. These labor laws were more humane than
many miners faced in the early 20th century!
Rio Tinto is still being mined today. Now the miners are working in open pits, rather than the tunnels of the ancient Romans. Millions of tons of black slag remain from Roman smelting operations. The slag contains small amounts of gold and silver, as well as copper, showing that the Romans were interested in these precious metals.
Miners today are mining brassy yellow copper "sulfide" minerals such as chalcopyrite. The sulfides were more difficult to smelt than the green and blue copper "oxide" minerals used by the Sumerians. The Romans were fortunate that the oxide ore was closer to the surface, and that there was a great deal of it.
The Romans did find a way to use the sulfide ores, although the process was very slow and probably produced little copper. They collected water that seeped through the mines. Copper dyed the water blue. The sulfur in the minerals turned into a combination of oxygen and sulfur called "sulfate". Sulfate in water makes sulfuric acid. This blue water was called chalcanthus by the Romans. When dried to make a copper sulfate mineral of the same light blue, that mineral is called chalcanthite. The Roman Empire's expansion and wealth depended on mines outside of the boundaries of the original Roman city state. Exploration for new mineral wealth was often the motive for Roman military expansion. Julius Caesar, for example, sought to increase his personal fortune by controlling the tin deposits of Cornwall, when he invaded Great Britain.
During most of the time up to the Roman empire, sufficient copper ore was available to meet the needs of the Mediterranean world's demands. However, the ore of Rio Tinto that could be exploited by Roman technology was exhausted by the fall of the Roman Empire. Rio Tinto became a ghost town. Barbarian invasions of the Fifth Century A.D. pushed Europe into the Dark Ages. Europe became a chaotic and dangerous place. Mining and metallurgy, like the rest of European culture, froze in place for centuries.
In order to smelt "sulfide" minerals, that is minerals made of copper, iron, lead and zinc chemically bound to sulfur, they have to be heated and "oxidized" first. The more easily smelted ores were exhausted by the time of the fall of Rome. The Moors lived in southern Spain during the Middle Ages. They used copper for cooking utensils and for ornaments. To continue to mine the still vast sulfide ore deposits of Rio Tinto, they developed a new process. They collected the ore, broke it into pieces, and piled it into heaps. Water was allowed to seep down through the heaps. The water was then collected. This technique is called "heap leach." The resulting solution contained copper in the form of copper sulfate. There was far more copper in the water than in the mine water collected by the Romans. Iron was placed into the water containing copper sulfate. A reaction occurred, in which the iron dissolved into the water, and copper precipitated where the iron had been.
Copper
Metallurgical Extraction Exercise
With iron being used for most weapons and tools, Rio Tinto was able to keep up with Moors' copper needs. However, the Spanish under King Ferdinand and Queen Isabella drove the Moors out of Spain in 1492. Interested in mines in the New World, the Spanish ignored the Rio Tinto district. However, other Europeans found that Rio Tinto was still richer than any mine in their district. The Spanish government leased the mine to a succession of Europeans.
In 1873, the London firm of Matheson and Company bought the mines. The new prosperity of Rio Tinto was brought about by a great new innovation in smelting sulfide ore. Heap leaching is very slow. It may take years to get enough copper sulfate solution. However, miners discovered that if the ore was burned or roasted before leaching, as much copper could be collected in 6 months as in 3 years with unroasted ore.
There were drawbacks to the new process, however. Roasting the sulfide ore released hydrogen dioxide gas. Clouds of this gas choked the miners and smelter workers and killed all the vegetation around Rio Tinto for up to 15 miles. This same problem has occurred around other copper smelters.
It was discovered, however, that the sulfur was also a valuable commodity. Now the sulfur is collected, to be sold to other industries to make sulfuric acid. Sulfuric acid is one of the most useful and important chemicals in the world.
Geology
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