Pocketed like crazy. Meteorite? Metal ore of some sort? Little heavier than any other rock its size. Feels like a rock looks like melted metal with air pockets. Any ideas?
It appears to be slag from a Smelting Furnace. As far as the make-up (composition) of it, it is hard to say. Where found and how found may help and if there are/were any Gold, Silver, etc. found near the location and any mines.
If you can clean it up a little better and take some pics of the specimen up close, we might be able to determine what it is. If a warm water and soap bath does not work, then you may want to get a small container of Muriatic Acid to clean the specimen with. Just make sure that you do the cleaning outside and wear rubber gloves. If the specimen is slag, then it is likely that there is some type of heavy metal the creek or surrounding area or an old mine somewhere upstream where the same was mined out and smelted. There is no reason to smelt unless you are getting some metals of value!