Mining for metals began as early as 12,000 years ago in the Stone Age in Upper Silesia, in present-day Poland, research on peat bogs has found.
Scientists found the evidence for mining in the ancient layers of bog in Miasteczko Śląskie near Tarnowskie Góry in southern Poland. The bog trapped the impurities that prehistoric people washed from the metal ores, researchers say, showing their findings in an exhibition at the Centre of Silesian Culture in the town of Nakło Śląskie.
Peat bogs are formed when dead vegetation falls onto waterlogged ground. Fine layers of dust and minerals can get trapped in these layers. A combination of archaeological, geological, geomorphological, physical and chemical analyses of the Polish bogs in Miasteczko Śląskie showed that these impurities were likely to be from mineral ores.
Because peat bogs layers gradually build up, the scientists could calculate the time since the mineral dust settled in the bog. They used radiocarbon dating to find the age of the layers. They found that the mineral deposits had been accumulating since the end of the Mesolithic, 12,000 years ago. The previous earliest estimate for metal mining in the area was the Neolithic.
In addition to the mineral dust, the researchers found other traces of past mining activity.
"We started to research this and the first thing we found was that the lead contamination correlated with contamination with charcoal used as fuel in furnaces," said Leszek Chróst of the Gliwice Research, Measurements and Ecological Expertise Laboratory in a statement.
Lead and iron smelting evidence, including nuggets of iron, in the bogs suggests that these were active industries as long as 2,000 years ago.
The findings are exhibited alongside research that found evidence of silver and zinc mining dating from the 12th Century, with evidence also discovered in peat bogs. Researchers found traces of malachite, cuprite, nuggets of precious metals such as gold, hematite and zinc ore, according to Grzegorz Rudnicki of Society of Friends of Tarnogórska Land from Tarnowskie Góry.
Prehistoric mining in Poland was known for materials such as flint, such as at the large Krzemionki flint mine near the southern town of Ostrowiec Świętokrzyski. The evidence of metal mining suggests that more advanced mining industries were present in the region much earlier than thought.