Is the shiny object a metallic mineral? The great majority of these on Earth are oxides and sulfides of iron---magnetite, hematite, and pyrites (fool's gold). This isn't a bad bet for Mars, too. We know the planet has substantial iron. It's famous red color is caused by the oxidation of iron.
I looked through literally hundreds of picturess of each of the above named minerals, on Google image. I found none that looked like the object photographed on Mars, nor that suggested that any of them would be expected to assume the weird, branching shape, suggested by the photographs made by Curiosity.
Edited by bison, 09 February 2013 - 11:20 PM.