BY W. N. BENSON. 453 



is not definitely marked. The component minerals are orthoclase 

 and quartz, and do not show much strain-effect. This rock 

 may belong to the same ancient series as the inclusions in the 

 Gerringong dyke. 



iv. Bowling ite at Dundas and elsewhere. 



Considerable difficulty was experienced, in the study of the Dun- 

 das inclusions, in the determination of the decomposition-products 

 of olivine. The most common material is a green felted mass of 

 very fine fibres, and this was doubtfully referred to pilite, actino- 

 lite, anthophyllite and talc*. 



In examining, in Paris, Prof. Lacroix' collection of slides illus- 

 trative of his work "La Mineralogie de la France et ses Colonies," 

 it was found that the bow^lingite of that collection was identical 

 with the decomposition-product in the Dundas rocks, which, also, 

 is the usual product of olivine in all the basalts in the Sydney 

 district. The mineral is a hydrous silicate of iron,magnesia, and 

 a varying amount of alumina. Prof. Lacroix thinks it is probably 

 identical with the platy mineral, iddingsite ; but the name 

 bowlingite should have priority, Tt is distinguished by its 

 strong pleochroism, and birefringence, combined with a straight 

 extinction. 



Proc. Roy. Soc. N. S. Wales, 1910, p.509. 



