Laboratory testing of the white dust which affected a number of properties and vehicles during roadworks in Eden has revealed it to be lime or hydrated lime that has transformed into calcite.
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A sample was sent by Cr Robyn Bain to a Canberra laboratory which then sent it on to Greencap in Adelaide as the South Australian laboratory had the equipment needed to test such a sample.
Principal consultant and senior mineralogist at Greencap Michael Till reported that the sample consisted completely of calcium carbonate ('calcite').
"Although calcite occurs naturally as marble and limestone, the particles in this sample are not considered to be rock particles. It is very likely that the calcite was originally calcium oxide (lime) or calcium hydroxide (hydrated lime). These two lime products readily absorb carbon dioxide from the atmosphere to form calcium carbonate," Mr Till explained.
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The good news is that it can be removed.
"Now that it has converted to calcium carbonate it will be relatively easy to remove. It will gradually dissolve in vinegar or other weak acids - possibly lemon juice. It will dissolve instantly (with fizzing) in dilute hydrochloric acid (pool chemical)," Mr Till said.
However the bad news is that in its earlier form as lime, is was corrosive and especially to aluminium metal, Mr Till said.
This brings into question the effect on solar panels and roofs during the time the dust was in its corrosive state. There is also the affect it may have in its current form on the take up of sunlight on solar panels.
Cr Bain said some residents were reporting a decrease in output from their solar systems although it could be hard to prove as it is dependent on the amount of sunlight on any one day.
In the meantime council is preparing a report on the matter which Cr Bain hopes to have within the next 10 days.
"We want to see what will happen with the council report," Cr Bain, who has been meeting regularly with the affected residents, said.
"What we do know is that at the point of testing it is calcite. What we saw visually after the rain (soon after the roadworks) was that the dust crystalised. At no stage has the event been disputed," Cr Bain said.
Mr Till was able to provide reassurance that calcite was "definitely not hazardous".
"All toothpaste would have it added as a mild abrasive. Also many calcium supplements from the pharmacist would have it as a source of calcium. If it is swallowed, our stomach acid would dissolve it very quickly," Mr Till said.
