X-ray technique used to detect unseen gold

August 25, 2013 

Working with Canadian company Mevex, the Commonwealth Scientific and Industrial Research Organisation – Australia’s national science agency – has conducted a pilot study that shows that gamma-activation analysis offers a much faster, more accurate way to detect gold than traditional chemical analysis methods.

This will mean mining companies can measure what’s coming in and out of their processing plants with greater accuracy, allowing them to monitor process performance and recover small traces of gold – worth millions of dollars – that would otherwise be discarded.

GAA works by scanning mineral samples – typically weighing around half a kilogram – using high-energy X-rays similar to those used to treat patients in hospitals. The X-rays activate any gold in the sample, and the activation is then picked up using a sensitive detector.

This method is two to three times more accurate than the standard industry technique, which requires samples to be heated up to 2,192 degrees Fahrenheit. csiro.au via eurekalert.org

Earliest iron artifacts came from outer space ore

Researchers have learned that ancient Egyptian iron beads now at Britain’s University College London’s Petrie Museum were hammered from pieces of meteorites – not iron ore. The objects also predate the emergence of iron smelting by two millennia.

Carefully hammered into thin sheets before being rolled into tubes, the nine beads – which are more than 5,000 years old – were originally strung into a necklace together with minerals such as gold and gemstones, revealing the high value of this exotic material in ancient times. The study is published in the Journal of Archaeological Science.

UCL archaeology professor Thilo Rehren, lead author of the paper, said: “The shape of the beads was obtained by smithing and rolling, most likely involving multiple cycles of hammering, and not by the traditional stone-working techniques such as carving or drilling, which were used for the other beads found in the same tomb.”

The study shows that in the fourth millennium B.C., metalworkers had mastered the smithing of meteoritic iron, an iron-nickel alloy much harder and more brittle than the more commonly worked copper, developing techniques that went on to define the iron age.

The beads, from a predynastic cemetery in Lower Egypt, were already completely corroded when discovered in 1911. As a result, the UCL team used X-ray methods to determine whether the beads were actually meteoric iron. ucl.ac.uk via eurekalert.org

Causes of bad air in China identified

What are the sources of air pollution responsible for Asia’s infamous atmospheric brown clouds?

Almost 80 percent of air pollution involving soot that spreads from China over large areas of East Asia – affecting human health and fostering global warming – comes from city traffic and other forms of fossil-fuel combustion, according to a study in the American Chemical Society’s journal Environmental Science & Technology.

Orjan Gustafsson, of Sweden’s Stockholm University and colleagues from China, South Korea and the United States used a powerful carbon-14 identification method to trace fully four-fifths of the black carbon emitted in China to incomplete combustion of fossil fuel such as coal briquettes used in home cooking stoves and automobile and truck exhaust. acs.org via eurekalert.org

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