A stone forest is a formation of soluble rock, which was dissolved by meteoric water until it formed pointy and thin pinnacles. Such structures are often named stone forest or pinnacles, often in combination with a geographic name. In China they are called shi lin (Chinese: 石林; pinyin: Shílín) after the stone forest Shi Lin in Yunnan Province. Often the term stone forest is used for the whole formation while pinnacle is used for a single tower.
The pinnacles are a special form of karren or lapies. This are forms which are a result of solution of soluble rocks, so all different versions are karren, while pinnacles are the subtype which forms, well, pinnacles. The term Karren is German, because karren were first described in the Austrian Alps. This type of karren is called Spitzkarren (pointy karren) in German.
Pinnacles are found only in tropical karst. The amount of solution requires tropical rains and high temperatures, frost on the other hand would easily destroy the fragile structures. And as solution is quite high, the pinnacles are dissolved quite fast, such structures do not live very long (in geologic terms) and are thus rather rare.