These are mountains of naturally-evaporated sea salt and are part of the Cheetham Salt Fields north of Adelaide and adjacent to St Vincent's Gulf.
I'd not really thought much about salt previously, but a little research reveals that it is used for supressing dust (being sprayed on in liquid form), as an essential part of stockfeed, as a method of curing hides and skins from spoilage prior to the remaining tanning process, as a vital ingredient in the pharmaceutical industry (whether used in preparation of dialysis solutions, cosmetics or health products), as swimming pool additive, as well as being used in the food industry and consumed by us locally as well as being exported overseas.
The salt you see above is double washed, dried, sieved and graded (to give consistent particle sizes) before it ends up in our pantries.
Here you can see the "fields" of salt water prior to evaporation
Sunset over the salt fields (posted earlier this year)
Joining others appreciating sky scenes at Skywatch Friday
Visit http://skyley.blogspot.com.au/ to see many more.