We did it! The boys are feeling somewhat better and we managed to squeeze a main lesson into our rather busy day. I don't have pictures; we mostly looked at pieces of granite as well as mica and quartz and talked about the composition of granite and how it is formed.
Earlier this year I picked up a complete classroom sampler of 50 rocks and minerals at the thrift store. It seemed spendy at $15 (we later found it online at $29 + s/h so we did rather well), but my rock hound really wanted it and I thought it might come in handy for this block, and already on day one it has. After hearing that the Romans used mica (Muscovite) as window glass they boys held up our specimens to the light and were able to see that they definitely were transparent and would serve that purpose well. The piece of granite in the sampler also showed the mica, quartz, and feldspar components better than the pieces of granite we had chosen from our own collection.
I decided that the boys were feeling well enough to attend park day, however the weather wasn't cooperating so a few of our park day friends came to visit us at our home. All three families already had children with the same cold as the children were all together on Halloween. We had a really nice visit and could hardly believe that it was Friday already; the week flew by!