Gunpowder tea is a green tea. It is mainly produced in Zhejiang province. Green tea there is harvested and goes through steaming, drying and rolled into tiny nuggets or pellets. I suppose it got its name as it might have resembled gunpowder pellets that were used some time ago.
It is interesting that the rolling of these tea leaves resemble the rolled up tea leaves of Taiwan high mountain tea as well as TieGuanYin oolong tea. I remember, when I was in Alishan Taiwan, the tea was also placed in a large cloth bag and the bag was compressed and rolled around in a machine, so that the leaves are rolled into a nugget/pellet shape. I suppose gunpowder tea is also rolled in this way but I was told that some gunpowder tea from Zhejiang uses the very old traditional method of hand-rolling each individual tea leaf by hand. I personally believe that among the green teas that are produced in China, gunpowder tea is one of the driest form of green tea, and if kept properly, is able to store well for a few years.
I have also read that good gunpowder tea is characterized by the high shine on the tea pellets as well as the tight roll of the tea leaf. If you do a search on the net, there are also gunpowder tea produced and sold in Taiwan and Sri Lanka. I also read that in Morocco, gunpowder tea is served with mint and sweetened.
How's the taste? I took about 10 pellets and brew them in a regular mug. The tea color is yellowish - like a regular green tea brew. You will also observe that the gunpowder tea unfurl to whole tea leaves when you brew a cup. I usually let my family taste new teas and the feedback I got from one of my girls is that there is a slight smoky aroma and taste. I myself found it slightly sweetish but without the floral notes found in Longqing green teas. Quite a delicious tea actually. I have yet to verify whether the gunpowder tea underwent a roasting stage but Yunnan Sourcing in his Zhejiang gunpowder tea page stated that the tea was roasted during the processing stages.
Gunpowder tea is an inexpensive tea. It is very suitable to bring a small pack when you are on the road. Just pack it in a tiny bag and there are no worries that it would break or damage easily like other green teas.