Because ink in a pen would be seperated into it's different components on the chromatography paper. Graphite pencils just... don't dissolve like that, they aren't soluble like ink. Graphite would not seperate on the paper, whilst ink would.
Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth's surface. These are the rocks that form at erupting volcanoes and oozing fissures.
