MINERALOGTCAL NOTES : No. VIII.— TOPAZ, ANGLE- 

 SITE, and other AUSTRALIAN MINERALS. 



By 0. Anderson, M.A., D.Sc. (Edin.), Mineralogist. 



(Plates Ixxix.-lxxxi.) 



TOPAZ. 



Carpet Snake Creek, near Tokrington, N. S. Wales. 

 (Plate lxxix,, figs. 1, 2.) 



The specimens here described consist of a small lot of isolated 

 crystals and a f ragment of matrix carrying one magnificent crystal 

 and several smaller ones; they were acquired by the Trustees 

 from Mr. Charles Bogenrieder, Mining Engineer. The figured 

 crystal, which measures - 8 x L5 x 3-25 cm., is loosely attached to 

 a matrix consisting of a clayey decomposition product (evidently 

 felspathic), quartz, wolfram, molybdenite, and a small quantity 

 of a purplish mineral too minute for determination, but which is 

 in ail probability fluorspar. The topaz is closely moulded on the 

 accompanying minerals, which therefore preceded it in most cases. 

 No information is available regarding the geological conditions 

 of its occurrence, but the hand specimen indicates a decomposed 

 pegmatite vein as its original home. 



The crystals are colourless, transparent, and of a uniform habit, 

 belonging to the Russian domatic type ; the crystallographic 

 characters are very similar to those of the Emmaville topaz. 1 

 The faces, with the exception of the base which is always more 

 or less rough, are highly polished and give good signals. Prism 

 forms are numerous, m (1 10) being the best developed ; 1(1 20) has 

 fairly large faces, but other forms in this zone are very narrow. 

 Of the domes, f (021) and d (201) are prominent, y (041) and 

 h (203) small; o (221) and u (111) are the most important 

 pyramids. An inteiestiug feature is the presence on the in faces 

 of very distinct, quadrangular markings, resembling the 



l Anderson— Austr. Mus. Rec, v., 1904, pp. 296-299; lb., vi., 1905, 

 pp. 83-85. 



