Viscosity of liquid anorthite

The viscosity of liquid anorthite has been determined over the temperature ranges between 1450°–1620°C and 820°–950°C. The high-temperature data agree well with previous experimental data and with predictions of the Bottinga and Weill model. The overall log (viscosity) versus 1/T relation exhibits pronounced and rather continuous curvature. The viscosity of anorthite is higher at any given temperature and more strongly temperature dependent than that of the anorthite-rich lunar compositions 14259, 14310, and 15418. The room temperature density of glassy anorthite (2.64 gm cm−3) and the thermal expansion coefficients of glassy and liquid anorthite have also been determined. The volume expansion coefficient for the glass is ∼1.8 × 10−5 °C−1, and that for the liquid is ∼4.8 × 10−5 °C−1. These values are used to relate the high-temperature flow data to the predictions of free volume theories.