It's a bit of a stretch to call this a common object. In fact, it's even a stretch to call this an uncommon object. It's actually more like the opposite of what we've written about here: A really weird object found in a common place. But we had to include it, because the world deserves to know about the existence of extraterrestrials.
Two Canadians sisters found this while digging in their backyard one day, as Canadians tend to do. At first they were confused by what it was, but they figured that they would find answers. They were wrong. An earth scientist told them that it was not a meteorite, and a gemologist told them it was not a gem of any known variety, or indeed a known mineral. In fact, to this day no-one has ever discovered what it is. Not of this earth, that's for sure.