Shown above is the state of our kitchen during week 5. Our contractor, Karl (a.k.a 'Fritz') came over to look at how the structure was put together in order to help us determine what kinds of beams we can use—carving the hole out of the ceiling that you can see at the top of the frame. I otherwise removed the wainscoting [a term that derives from the medieval German wagenschot or 'wall-board'] and removed the diving wall between the kitchen and downstairs bathroom.
The next few photos show changes to the 'library' walls as I first started removing their original faces. The walls we focus on here are the 'new' exterior walls, which were presumably added to the house at the time of the first addition.
Yes - that is vermiculite.
For those that aren't familiar with it, vermiculite is a hydrous phyllosilicate mineral resembling mica in appearance. When heated to to around 1000 degrees centigrade, vermiculite undergoes significant expansion and exfoliation.
Between 1919 until about 1990, over 70 percent of all vermiculite sold in the United States derived from a mine near Libby, Montana—often sold under the brand name Zonolite. There was also a deposit of asbestos at that mine, so the vermiculite from Libby was contaminated with asbestos. For this reason, most vermiculite insulation should assumed to be contaminated with asbestos. 
Fortunately, our vermiculite pre-dated the operation of the Libby, and so was not laden with asbestos. Still, when getting it all cleaned out, we've been careful to wear our masks and coveralls.
This next photo shows the state of our "woodworking and furniture restoration shop" (which will really be an upstairs office and guest bedroom).