G. J. Brush on Tephroite. 67 
lustre. The specimen received from Professor Breithaupt had 
the following physical and chemical characters—Color, dark-ash 
tosmoky-gray. Lustre, vitreous to greasy. Hardness, 6. Spe- 
cific gravity, 410 (Breit.). It was associated with franklinite 
and zincite; small specks of the latter species were so intimately 
mixed with the tephroite that great care was required to obtain 
the mineral pure for analysis, The zincite seemed to be dis- 
Cloizeaux has shown, from the examination of crystals in his 
toa cleavage plane, which seems to me to be perpendicular to 
th 9° 30’ 
2H==84° 19’ Red rays, hence 2E=159° 17 
82° 59’ Blue rays, hence 2 E=156/ 58’ in air. 
The indices of refraction of the oil employed were 1°465 for the 
red rays, and 1-479 for the blue rays. As my small plates were 
hot cut absolutely normal to the bisectrix, these measurements 
are sufficiently near those published in my paper to enable us 
to indentify the species, especially as the position of the plane 
of the axes, and the character of the dispersion is the same in 
th cases,” 
These important observations, in connection with the memoir 
y Professor Des Cloizeaux, before alluded to, demonstrate con- 
usively that the optical and crystallographic characters of the 
‘ Annales des Mines, 5th Series, se P. 24 
ces w. : es. G. J. B. 
ic an Aripescl bi ney on the anne plane was unquestionably due to 
* From a Wiles io sof Oe Siac! dated Paris, Feb. 19th, 1863. 
