Does placing your large hand on your square jaw help you come up with these inane thoughts? Yes, gypsum is used in Sheetrock (an also tofu, for that matter…) but it’s not mined in crystalline form, but rather found in sedimentary rock formations…
Your knowledge of the commercial world is fairly wanting Mr. Trail, but then you’ve never really had to pay for the roof over your own head… a living off expense account and the largess of your father in law has left you wholly unaware of what it takes to turn a profit…
The Daily Trail 
Yes, sir! If I were roasting in an underground crock pot, I’d sure spend my time discussing the genesis of sheet rock, for sure!
And just WHAT THE HELL are these losers doing, anyway? They seem to have totally forgotten why they came to the cave in the first place, why they are running, and where they are supposed to be going. Is Allen on drugs or is he letting his grandchild with the homework assignment take over the story line? We should notice that Tubby doesn’t even have a token place in the strip at this point, having been reduced to a black outline earlier. Perhaps he will show up again in the role of some B-film “screamer” when the bad guys start dropping a ladder down the sink hole.