306 





C. ANDERSON. 



rin relations : — 





Segments. 



Meas. b \ b 



I, v 



57° 27' | 



II, VIII 

 III, IX 



57 12 | Calc ' for r - twin 57 ° 18 '- 



IV, VI 



57 17) 



I, VIII 



62 43 . 



11, IV 



62 41 1 



IV, XI 



62 54 lOalc. for m-twins 62° 46 



VI, VIII 



62 39 



VII, IX 



62 45 J 



The only crystal unaccounted for in the above scheme is 

 X; it approximates to the position of an r twin to VIII 

 (meas. b A b 57° 6), which would make it a witness against 

 Goldschmidt's supposition. A small arrowhead twin is 

 planted on I and II, one segment being parallel to II, the 

 other with VIII ; an embryonal r-twin has settled on II, 

 one segment of the twin placing itself paralled to II. 



Oerussite from Muldiva. 



In the Australian Museum collection there are two 

 specimens of azurite from the Paisley Shaft, Muldiva, 

 Chillagoe District, Queensland ; the azurite, finely crystal- 

 lised, 1 is on a limonite matrix, and seated on the azurite 

 are small crystals of cerussite, many of them twinned. The 

 cerussite groups are scarcely larger than a pin's head, but 

 the faces give good reflections in the main, and four groups 

 were measured with the following results. 



Description of Groups. 



Group I (Plate LIII, fig. 5). This is a triplet of a type 

 common with cerussite and aragonite. The faces, idealised 

 in the drawing, belong to the forms c (001), a (100), b (010), 

 m (110), r (130), y (102), p (111). The value of <£ for the 

 three segments is 0° 0', 62° 41' and 117° 18' respectively, 



1 Anderson, Rec. Austr. Mus., vn, 1909, p. 278. 



