Explanation

It is a rock pyroclastic rock formed by compaction and consolidation of crystal chips, glass chips, rock chips and other pyroclastic materials with particle size less than 2mm formed during volcanic eruption. The cementitious material mainly consists of finer volcanic ash, which has various colors. Common colors include gray white, gray, gray green, yellow white, white, light purple, gray purple, gray black, etc. The appearance is often rough. According to the detrital composition, it can be divided into crystalline tuff, glassy tuff, lithic tuff and complex tuff. According to chemical composition, it is basaltic tuff, andesitic tuff, dacitic tuff, rhyolitic tuff and trachytic tuff. The minerals related to tuff include copper, iron, pyrite, uranium, potassium, boron, zeolite, etc. Some tuff is a good light and hard building materials due to its many pores. Some acid tuff rich in glass chips is a good raw material for cement mixing. A few altered tuff with moderate hardness (hardness 3-4), fine and uniform particle size (<0.01mm) and few dense and fine cracks is the materials of precious jade. For example, the famous Qingtian stone in Zhejiang Province and the chicken-bloodstone in Changhua are mainly altered rhyolitic tuff. Because of their colorful color, moderate hardness, good processability, uniform and fine texture, and containing pyrophyllite, seridte, diaspore and other minerals, they are superior raw materials for jade carving industry. After alteration of tuff, various clay deposits such as kaolin and bentonite can also be formed. China is rich in tuff, which is mainly distributed in the east.

Classification