‘Aussie kryptonite’ helps identify mineral deposits

Researcher Matt Shaw saved a sample of Plumbian orthoclase from his days working in Broken Hill’s Rasp mine. (Image by Matt Shaw, CSIRO).

Researchers at CSIRO, Australia’s science agency, are investigating the properties of plumbian orthoclase, a glowing green mineral that is part of the country’s mining industry revolution.

Plumbian orthoclase is incredibly rare, found exclusively around the outback mining city of Broken Hill. The word plumbian means lead-rich, and it’s the lead that gives the mineral its famous green appearance.

In fact, Broken Hill’s orthoclase has the highest lead content of its peers anywhere in the world.

Often called green feldspar and dubbed by scientists “the Aussie kryptonite,” some of Broken Hill’s plumbian orthoclase samples get misidentified as amazonite.

Although plumbian orthoclase doesn’t physically glow, CSIRO’s mineral resources team discovered it is mildly radioactive, not enough to hurt anyone but enough to read above background levels.

This lead-rich orthoclase, thus, is very useful as an indicator mineral, which helps geologists locate and assess the presence of certain ore deposits, such as the lead, silver and zinc deposits of Broken Hill.

Mining has been intrinsic to the Broken Hill area since Charles Rasp discovered silver there in 1883. Rasp formed the Broken Hill Proprietary, better known as BHP.

Geologists and mining experts disagree on what made the Broken Hill deposits so complicated, as it is a boomerang-shaped ore body, its highest point sticking out in the middle.

They agree, though, that the place is special as it is the only area on earth where plumbian orthoclase can be found.