Black tea remains the perennial favorite among tea drinkers. In fact, it still accounts for more than 90% of all tea sold in the West. The most oxidized of all tea types, black tea is generally stronger in flavor and contains more caffeine than other teas. Since black tea retains its flavor for several years, it has been an important item of trade for centuries, and was actually used as a form of currency in Mongolia, Tibet and Siberia during the 1800’s.