"Until at least the 13th century, “jade” in China was generally nephrite, a tough, white-to-green amphibole rock that was a favorite of stone carvers. The most important source was south of Hotan (Khotan) in the Kunlun mountains of western China; here, nephrite was recovered from both the White Jade and Black Jade rivers (Gump, 1962). Sometime in the 13th century, according to local lore as reported by Warry (Hertz, 1912), a Yunnan trader traveling through what is now northern Burma picked up a boulder to balance the load on his mule. When it was broken open, the brown-skinned rock revealed a vivid, “emerald” green material with the toughness of nephrite. The Chinese were captivated by this stone.
Also according to Warry, the Yunnan government sent expeditions to find the source of this unusual material in the 13th and 14th centuries, but they were unsuccessful. Although occasional small pieces of green jadeite would appear in China over the next 500 years, their origin remained a mystery until the late 18th century.

Enter the Dragon. In 1784, Emperor Qianlong (who reigned from 1736 to 1796) extended China’s jurisdiction into northern Burma, where Chinese adventurers soon discovered the source of the green stone. From the late 18th century on, considerable amounts of jadeite were transported to Beijing and the workshops of China’s foremost jade carvers. Emperor Qianlong preferred the rich hues of this “new” jade (jadeite), and soon the finest semi-transparent rich green fei-ts’ui (“kingfisher”) material came to be known as “Imperial jade” (Hertz, 1912).
A well-established route for jadeite from Burma to China existed by 1798. Although political and other circumstances forced several alterations in the original route, the “jade road” – from Hpakan through Baoshan and Kunming in Yunnan – operated until World War II."

--Richard Hughes

LATER: Lest my post subject be interpreted as too categorical, it was in reference to small jade trinkets likely to be found in markets.