GoFind60 ... are you sure it is lead ?
Lead is mallleable .. if you hit it with a hammer it will flatten out like a gold nugget or any other soft metal, alternately you may have found some Galena which generally is seen in various sized cubes, it tends to sparkle in sunlight, if it is hit with a hammer it will shatter into pieces.
Mercury it isnt .. as Mercury at room temperature is a liquid form and solid when frozen but interestingly when frozen it becomes one of the hardest metals known to man.
Another possibility ... Adelaide hills ... commonly a place where Silver has been found.
As for gold being where you found your specimen, there is a greater possibility if it is Galena because Galena belongs to the sulphides group like pyrites (fools gold), and the sulphides are found in the areas where you look for gold.