thanks for the replies. I would say the floor is kind of uneven. I think the floor is moist, but not wet. When I was clearing the area of junk, and lifted up an old large coleman cooler, there was moist black stuff - is that black mold? ouch!
The basement is partially finished in this way: it is a 30 x 30 area that had been compartmentalized into five rooms...
1) a very small tool and paint repository....foundation walls exposed, unfinished top space, and concrete floor surface
2) right next to this room, and delimited by a wall, is the room where the furnace is. There is maybe 10 x10 feet in front of the furnace for some storage items....this room has foundation walls exposed on the exterior side and internal walls delimiting the other rooms, top area unfinished, and concrete floor surface
3) three other rooms with finished sides, acoustical tiles on top, heat and electric; floor surface=wall to wall utility type of carpet.
The dust in the furnace room I referred to was dust from the eroding concrete that constitutes the floor mostly. then there is dust from the eroding foundation (fieldstone? limestone? -1882 vict) and mortar-like compound between the stones from the unfinished foundation walls close to and behind the furnace