Shoushan Stone

Shoushan stone, one of China’s most famous craft-carving stones, is mainly produced in the Shoushan basin in northern Fuzhou City, Fujian Province. Shoushan stone can be divided into four main categories, including the Tianhuang stone, Gaoshan stone, hibiscus stone, and Wenyang stone based on their production places. Significantly, the stone produced along the Shoushan river, also named Tianhuang stone, is honored as the “emperor of Shoushan stone” due to its great cultural and economic values. In gemology, Shoushan stone is classified as a colored gemstone. However, its common names are very complicated, which have been identified in more than 100 varieties by traditional custom.

Despite its complicated varieties, the mineral composition of Shoushan stone mainly includes kaolinite (e.g., kaolinite, dickite, nacrite), pyrophyllite, and illite group minerals. These clay minerals are the product of the hydrothermal alteration of felsic magmatic rocks in common. The Shoushan basin is a part of the Coastal Volcanic Belt in southeastern China. Significant volcanic activity during Late Mesozoic provided heat and hydrothermal fluids for alteration. In theory, Shoushan stone is formed in an epithermal hydrothermal environment (100–405 °C). It is difficult to obtain accurate syngenetic age results, so the exact age limits for the Shoushan stone formation remain uncertain. Studies have demonstrated that the Xiaoxi Formation of the Early Cretaceous is a critical formation containing nonmetallic deposits, such as pyrophyllite and alum (including Shoushan stone). Our study chose a caldera (Qishan) in the Shoushan basin as a typical section to identify volcanic sequences and lithofacies. According to the stratigraphic correlation from the Early Cretaceous in Fujian Province, samples from the Xiaoxi Formation at different locations are collected to obtain their chemical compositions. Combined with the geochemical results, the geological background is revealed to understand the formation mechanism of Shoushan stone. The Xiaoxi Formation is composed of altered and unaltered volcanic rocks. Based on the result of a stratigraphic section, the mineralization (i.e., alteration) age of Shoushan stone is constrained by the magmatic zircon U-Pb age (135 and 131 Ma) of the critical host tuff.