...Fig. 1. The system MgO–Al 2 O 3 –SiO 2 –H 2 O projected from H 2 O with the representing points of the relevant phases at high pressures. Phase “Pi”: Piezotite (Al 3 Si 2 O 7 (OH) 3 , Wunder et al ., 1993 ); Phase “egg” (Al 5 Si 5 O 17 (OH), Eggleton et al ., 1978 ). ...

.... Schulz H. Holzapfel W.B. ( 1978 ) High-pressure single-crystal structure determinations for ruby up to 90 kbar using an automatic diffractometer . Journal of Applied Physics , 49 , 4411 – 4416 . Daniels P. Wunder B. ( 1996 ) Al 3 Si 2 O 7 (OH) 3 , phase Pi (formerly piezotite...

... called because was formerly thought to be the poorly described synthetic mineral piezotite ( Coes 1962 ). The mineral has been synthesized at low temperatures and moderate pressures (500–650 °C and 4–5.5 GPa) ( Wunder et al. 1993 ) in the hydrous aluminosilicate system. The structure (Fig. 17...