I think your post is gibberish; isolation has little or nothing to do with how a room sounds, square rooms SUCK acoustically, and WTF is a coquina??!? Steve
coquina is a type of stone - this from an article on the subject:
"Coquina, a limestone conglomerate material named for the shells of the small mollusks it contains, was used as building stone in St. Augustine as early as 1598 for construction of a powder house. This was the beginning of a building tradition that extended into the 1930s along Florida’s Atlantic Coast."