Ferroelastic phase transition in SrA12Si208 feldspar at elevated pressure

Synthetic end-member strontium feldspar (SrAI2Si2Os) has been studied in a diamond-anvil cell at elevated pressures up to 10.3 GPa using energy-dispersive X-ray powder diffraction. Cell parameters have been refined between ambient pressure and 6 GPa. SrA12Si2Os undergoes a ferroelastic phase transition from the ambient pressure monoclinic space group 12/c to the high-pressure triclinic space group/1 at 3.2 __ _ 0.4 GPa. The transition appears to be first-order and the ferroelastic and co-elastic components of the spontaneous strain tensor have been calculated