How can you test if gold is pure? Some methods are more destructive than others

By Michael Cortie, Physics Discipline Leader, University of Technology Sydney

When it comes to gold, how pure is pure? And how does anybody know?

As recent revelations about the Perth Mint have shown, gold buyers and sellers take purity very seriously. Questions have been raised over impurities found in some A$9 billion worth of gold sold to the Shanghai Gold Exchange.

While the gold reportedly met the industry standard for 99.99% (or “4N”) purity, it failed to meet extra agreed specifications for the level of silver.

Read complete article

~	Why sitting down – and getting back up – might be the most important health test you do today

~	Trump can’t decide who to blame for a failing peace deal that would only lead to further conflict

~	In talking with Tehran, Trump is reversing course on Iran – could a new nuclear deal be next?

~	Tensions over Kashmir and a warming planet have placed the Indus Waters Treaty on life support

~	Warfare is Band of Brothers for the ‘war on terror’ generation

~	Trump’s tariffs: poor workers in countries like Cambodia will be among the biggest losers

~	Why the energy transition won’t be green until mine waste disasters are prevented

~	Leading by example: how the rich and powerful can inspire more climate action

~	Tove Jansson’s Moomin books explore the power of adventure and transformation

~	Why you don’t need to stress about cortisol ruining your waistline – or your face