16 recorj>s of the austrai.iax museum. 



Chai-.azuie. 



Near Glen Iiines, N.S.WalcK. 



(PI. v.. Wg. 1.) 



'I'lie fliabazite associated witli tlie crystals of calcite described above 

 forms a continuous crust on the surface of decomposed basalt. The pale- 

 yellow, translucent ci-ystals aie small, the average size being about that of 

 the head of an ordinary pin, and they form botryoidal or stalactitic 

 aggregates with a core of clayey decomposition products ; chabazite 

 apparently preceded calcite. 



The crystal faces besides being minute are iu)t brilliant and give 

 rather poor reflections, but the measurements made with the reducing lens 

 of the goniojueter, were sufficient to identify the two fo}'ms s (0221) and 

 / (1123) for which resftectively the angle p was found to be 66° 53' 

 (calc. 68'' 16') and 86^ 89' (calc. 3^° 5-t'). Tlie only other form present 

 is /• (1011) from which however, no reflections were obtained, but there 

 can be little doubt of its presence. The crystals are symmetrical pene- 

 tration twins about the vertical axis, and the mineiul would therefore be 

 described as the phacolite variety. The twin structure is cleai'ly revealed 

 by the re-entrant angles in tlie equatorial region ; these ai'e pi'oduced by 

 the meeting of the /• and /; faces. The distribution of the faces of s is also 

 a consequence of twinning. On the coplauar faces t and f^ there is a 

 de[)ression, deepening towards the apex and with boundaries approximately 

 parallel to the edges of the composite face. 



To coiiHrm the identiflcation the water and silica percentages were 

 determined and found to be 21'9l and 45'71 respectively; this is in close 

 agreement with the published results of chabazite analyses. 



VESUVlANriK. 



Arramagong, N.S.Wales. 



(PI. v., figs. 2, 3.) 



I am informed by Mr. G. W. Card, Curator of the Mining and 

 (ieological Museum, that this mineral occurs in serpentine, close to its 

 junction with granite at the Trigonometrical Station, Arramagong, 

 between Gi-enfell and Young. The crystals are prismatic, small, the 

 Hgured specimen measuring 6 X 1'5 mm., honey-brown in colour and 

 transpaient. The forms present are r (001), a (lOO), m (110), f' (120), 

 <h (•^•>'>). /' (111), I (:>'il), ••'• (I'il)- <>l' <l't' prisms, which are' striated 

 vertically, /// is the largest,/ is narrow and (f, wiis observed only once. 

 The faces of s show slight stria? parallel to their intersections with // ; 

 /) gives ver}' good reflections and from the angles obtained the axial ratio 

 was calculated. From twelve faces the average value of p whs f\)und to 

 be 37^ 17' 35" (limits 37° 16'— 37° 20') therefore the vertical axis is 

 •53853. 



