I'll just weigh in to reinforce both what Grymm and Capt. Sterling are saying here. A few years ago Deb Peterson (see Sterling's link) held a symposium on period coffee, tea and chocolate, and the up-shot was, based on serious research by people passionate about the subject, that tea bricks don't show up until way too late for any of us here to be using them. When I can get to it, I'll look at my symposium notes and see if I can't find the name of the presenters and bibliography.
We've beaten that horse (and others) way beyond resurrection in the later 18C forums, trying to find evidence for tea bricks. If we haven't found it yet, and we've had years to cover it, and many, many people asking the same questions we get here, it probably didn't exist yet in the western world, except perhaps as a curiosity. The only way that is likely to be overturned is to find first person evidence in a diary, inventory or picture, which documents not only it's existence, but consumption.
Oh, and I'd like to point out that both the 18C Woman and SavoryFare2 lists do not have complete archives from their beginning, as both have undergone changes over time and some of the older discussions have been lost (SavoryFare2 was once SavoryFare). If anyone has a clue as to how to access that information, please share!
Jen Dobyns