(500, 0.38)(350, 0.19)kyaniteandalusitesillimanite(760, 0)(795, 1.0)Phase Diagram for Alumninosilicate PolymorphsTemperature (°C)Pressure (GPA)00.20.40.60.81.0400500600700800

The phase diagram above shows the conditions that are needed to form different aluminosilicate minerals. The temperature TT, in degrees Celcius (°C) is shown on the horizontal axis, and the pressure PP, in gigapascals (GPA), is shown on the vertical axis. An equation of the boundary line between the andalusite and sillimanite regions is approximated by the equation below. What is the meaning of the TT-intercept of this line?

P=0.00146T+1.11P=-0.00146T+1.11