Sydney dust storm analysed by Museum mineralogist

Minerals don’t always come in large and attractive crystals, but can be as fine as dust. Sydney’s record-beating dust storm gave Australian Museum Mineralogist Ross Pogson an opportunity to study these ‘dusty minerals’. He carefully brushed some dust off the bonnets of cars in the Museum’s car park early this morning and analysed the sample with an X-ray Diffractometer, adjusting the machine to give the best results for these very fine-grained particles.

The high and low peaks which slowly revealed themselves on the computer screen showed familiar patterns to a trained eye. Preliminary results show the major mineral in the dust is Quartz (silica), together with minor amounts of the clay mineral Kaolinite (aluminium silicate-hydroxide) and a very fine-grained mica (potassium, aluminium silicate-hydroxide). The red-brown colour is from goethite (iron oxide-hydroxide), which is so intensely coloured that only a small amount is needed to give the dust a good colour. Unfortunately the mineral contents do not allow exact origins of the dust to be determined, but it is believed to come from the general central Australia region.

Story by Ross Pogson