Solid Solution Relationships Between Wolframite and Scheelite

In zoned crystals of ferberitic wolframite containing scheelite inclusions from near Alice Springs, North Territory, almost complete solid solution is recorded between these two components at elevated temperatures. Retention of very small amounts of scheelite component in solid solution under atmospheric conditions is deduced, and, due to the relatively large ionic radius of calcium, significant variations in (111) spacings result. Without chemical analyses these (111) spacings may give incorrect mineralization temperatures. Nevertheless it is shown that values closer to the theoretical may be obtained after maintaining crystals for prolonged periods under increased vapor pressures and temperatures.