in my experience, darker, pliable hash is the most potent... The only hash I've ever smoked is bubble and I've had lots of differnt types from light tan conctrete-like rocks to extremely gooey black/dark brown chunks... the only real way to test hash is to smoke it (the longer it lasts, the better it is...also you want it to bubble/melt as much as possible...taste is also a factor)...