The first two pictures look like slag, the third one looks crystalline to me. Perhaps the specimen is a composite of slag with something else that did not melt in the furnace. Is there a distinct boundary between the two areas?
I also think the first two are probably slag. Your third image of a white columnar aggregate may be Tremolite. Compare here: http://www.mindat.org/photo-33180.html If it is Tremolite, it may be fluorescent so if you have a SW or LW source you may want to check this. Good luck.