Well, I have an urban/suburban beehive (Victorian neighborhood) in a
middling city (San Jose, Ca.), and the propolis in my hive is hard, ranging
from dark brown color to a pale amber.
 
The "bubble gum" consistency you mention makes me wonder if this might
be something other than a natural resin.  Anyone know if bees actually go
after chewing gum? ;-)  Do they necessarily distinguish between resin and
say, something like a caulking compound?
 
Jane