Abstract
In situ synchrotron-radiation powder X-ray diffraction was applied to a natural vesuvianite with P4/nnc structure, (Ca19.0Na0.259K0.012)∑=19.271(Al9.089Fe3+1.376Ti0.341Mg2.156Fe2+0.216Mn0.008)∑=13.186P0.098(Si17.977Al0.023)∑=18O70.208(OH)7.792 by means of the diamond anvil cell technique up to 27.9 GPa at room temperature. The isothermal pressure–volume relationship of vesuvianite was well fitted by the third-order Birch-Murnaghan equation of state with V0 = 2865.9(4) Å3, K0 = 143(3) GPa and K0′ = 5.2(4). The compressibility of the structure is anisotropic with βc = 2.76*10−3 GPa−1 > βa = βb = 2.14*10−3 GPa−1. Thermoelastic properties of vesuvianite were compared and analyzed with its structural analogues (grossular, hydrogrossular and epidote).