When I took a college course about dinosaurs a few years ago, I took the opportunity to confirm what a family member told me when I was very young. Someone had given me a small lump of irregularly-shaped rock and said it was a dinosaur bone. It certainly looked like some kind of fossil, and in 2003 I brought it to my professor to see if he knew what it was.
If my professor was sure of anything, it was that my specimen was not a fossil. It looked like a bone, sure, but it was just a small rock that had formed in a way that looked bone-like. It did not have the honeycomb-like internal structure that is a tell-tale sign of fossilized bone. Such mistakes are easily made, though, and it seems that a similar fossil-like rock has been making a bit of news lately.
This past weekend, DL-Online posted a story about a "baby dinosaur" skull discovered by Minnesota rockhound Mitchell Voss. Held the right way there is something dinosaur-like about the image on the rock, but this resemblance appears to be due to irregular swirls on the rock. This is similar to the famous (and now lost forever) Old Man of the Mountain from New Hampshire. While the side of the mountain appeared to present a human-like face, the "Old Man" was just a series of cliff ledges that, viewed from the right angle, looked like a human face. The same phenomena is at work with this "baby dinosaur", and I have no doubt that an examination of the internal makeup of Voss' find will reveal it to be a rock.