302 KECORDS OF THE AUSTRALIAN MUSEUM. 



increasing more rapidly in the direction of the prism faces than 

 towards the angles. The structure of many of the Bimbowrie 

 specimens is such as to favour this view. According to Lehmann 

 crystals forming in a solution grow most rapidly on the edges, as 

 diffusion currents promote more rapid growth of the angles. But 

 chiastolite is formed by the agency of metamorphism in a pre- 

 sumably solid rock, permeated, no doubt, by heated water and 

 gases, and quite different laws of crystal growth may prevail 

 in such cases. Referring to fig. 2, where the foreign matter forms 

 nearly one half of the entire mass, it seems scarcely admissible, 

 considering the large amount of inert matter, to speak of the 

 crystallising force " constraining " the inclusions to assume a 

 certain regular position. But, by irregular growth, reentrant 

 angles are formed, and in these a considerable amount of clay- 

 slate is caught up, some being incorporated in the body of the 

 crystal, but the bulk being more nearly related to the contain- 

 ing rock mass. Further metamorphic action may render the 

 union of mineral and "inclusion " more intimate, but that each 

 is semi-independent is apparent from the result of weathering 

 seen in fig. 4. 



Prof. Liversidge^ states that chiastolite occurs in granite rock 

 at Arnprior, Boro, near Goulburn ; in small crystals in slate near 

 Modbury, Shoalhaven ; and near Tumut, in micaceous slate or 

 schist. Mr. E. F. Pittman has found it occurring as small crystals 

 in slate, at the Euriowie Tin Field, Barrier District. 



Chiastolite slates, containing small crystals of that mineral, are 

 also known from Queensland, Victoria, and Tasmania. It is 

 interesting to note that the Geological Survey of New South 

 Wales possesses a microscopic section of an aboriginal stone axe, 

 from Strathbogie, Scone, Co. Gough, New South Wales, contain- 

 ing small crystals of chiastolite, some of them very well formed.^ 



3 Liversidge— Min. New South "Wales, 1888. 



* David— Proc. Linn. Soc. N.S.W., (2), ii., 4, 1887, p. 1081. 



