88 



RECORDS OF THE AUSTRALIAN MUSEUM. 



A fine crystal (PI. xviii., fig. 5) measuring 7 mm. X 9 mm. x 7 

 mm., and perfectly clear and colourless was measured on the 

 goniometer. As the faces are very irregularly developed and one 

 side of« the crystal is broken, the crystal is di-awn in ideal 

 symmetry, but so as to show the habit as nearly as possible. The 

 prisms m (110) and I (120) are about equal in size and striated, 

 but the images are good. The brachydomes /(021) and y (041) 

 are relatively small, while the macrodome d (201) is unusually 

 large and brilliant. The base is large and smooth. The pyramid 

 o (221) is small, u (111) and i (22.3) large and brilliant. 



The co-ordinate angles found are tabulated below. 



Bell Mount, Middlesex, Tasmania. 



Mr. Petterd informs me that topaz occurs at Bell Mount in a 

 very decomposed quartz-porphyry, also as pebbles weathered out 

 in the drift ; it has not previously been recorded from this locality. 

 Two crystals, both colourless and transparent, were examined ; 

 one is much worn and broken and unsuitable for goniometric 

 determination. The other (PI. xviii., fig. 6) has good prism and 

 dome faces but the pj^ramids are dull and were measured in the 

 position of maximum illumination. The base is absent. The 

 crystal measures 13 mm. X 10 mm. x 11 mm. 



