Black vinegar is an inky-black vinegar aged for a malty, woody, and smoky flavor. It was first popularized in East Asia, particularly southern China, where in the city of Zhenjiang it became known as Chinkiang vinegar. It is made from rice (usually glutinous), or sorghum, or in some combination of those, perhaps including wheat and millet.
A very different black vinegar is made on the central plains of China and is most associated with Shanxi province. Called specifically Mature Vinegar (simplified Chinese: 老陈醋; traditional Chinese: 老陳醋; pinyin: laochencu), it is made from sorghum, peas, barley, bran and chaff and has a much stronger smoky flavor than rice-based black vinegar. It is popular in the north of China as a dipping sauce, particularly for dumplings.
Some claim that black vinegar has numerous medicinal properties, such as a tonic which may lower blood pressure and cholesterol levels. In Japan, kurozu is a somewhat lighter form of black vinegar, made just from rice. It has been marketed as a healthful drink.