I don't know what the black object could be. It could be anything.
Unfortunately, there is not enough detail showing to make out what the object is.
Also, contained in this particular HazCam image are some very interesting shapes and other objects that do not appear natural at all.
The objects contained within a yellow ellipse is where Curiosity has rolled over the surface.
Viewing of this image with an optical magnifier is an essential requirement in order to determine the very small detail object detail.
I have darkened the image by approx. 60% and improved the sharpness and edge definition.
"All truth passes through three stages. First, it is ridiculed; Second, it is violently opposed; Third, it is accepted as being self-evident."
Arthur Schopenhauer
Credit to Scott Waring @ UFOsightingsdaily
http://mars.jpl.nasa.gov/msl-raw-images/proj/msl/redops/ods/surface/sol/01183/opgs/edr/rcam/RLB_502516568EDR_F0511430RHAZ00313M_.JPG
http://www.ufosightingsdaily.com/search?updated-max=2015-12-05T13:30:00%2B08:00&max-results=10&start=20&by-date=false
The whole universe is to the observable universe, as the observable universe is to an atom. - Alan Guth
