gems, beryl, emerald, China, Sichuan, Jieka

Emeralds were discovered for the first time in the Jiajika area of Sichuan Province, known as the largest hard rock-type rare metal mining region. Geological surveys, optical microscopy, and electron microprobe analyses revealed two forms of emerald occurrence: one as emerald-bearing coarse-grained beryl without independent grains, and the other as fine-grained beryl containing emerald. In vein No. A, the edges of coarse beryl showed significantly higher concentrations of Cr₂O₃ (0.40%–0.63%) and CaO (0.12%–0.41%) compared to the core, indicating typical emerald composition. The emeralds in Jiajika exhibited high but variable CrO and FeO contents, along with low V₂O₃ levels—features consistent with most emerald deposits. The chromophores Cr and Fe originated from Triassic Xikang Group sand shale, while major elements like Be, Si, and Al were sourced from intrusive acidic granite or pegmatite. Comparative analysis of emerald deposit types, along with the regional tectonic background, magmatism, and mineralogical traits, suggests the potential existence of a deep ore-forming fluid source in the Jiajika area, supporting the need for further deep exploration to guide mineral prospecting.