There are a few ways to try and identify already split firewood. To start, the most common types of firewood in North America are pine, oak, sycamore, elm, cherry, maple, hickory and ash. With these in mind, when you check the firewood you should look for leftover bark, leaves, color and end grain. Wood types like oaks and maple wood have unique bark making them easier to identify. For the leaves, wood types like pine will have telltale needles vs actual leaves making identification easier as well. If you can’t use either of these methods, you will always be able to check the color and the grain of the wood. End grain is usually the most reliable, and you can research the visuals of popular grains of the wood types mentioned above to start.