188 THE MINERALS OF TASMANIA. 



bs related to the hydrated fluorine compounds fluellite 

 and prosopite. (Ca F„ 2 Al (F, OH) 8.) It may be 

 remarked that a pale green-coloured variety occurs in 

 Utah. (See Hillebrand, Am. G. Sc, 7, 53, 1899.) 



Under the influence of the emanation of radium bromide 

 this altered topaz exhibits some peculiarities which are 

 worthy of note. With radium bromide (of 1,800,000 

 intensity), using a thin sheet of metallic aluminium as a 

 filter to the natural glow of the preparation which is 

 interposed between the assay and the cell containing the 

 radium, a pale but very distinct greenish light is observed 

 This is apparently characteristic, as all the specimens thus 

 examined gave the same result ; but after the mineral 

 was strongly heated in the platinum forceps it did not 

 in any manner respond to the radium emanations. The 

 substance under examination continued to show the phos- 

 phorescent light for a considerable period after removal 

 from the vicinity, and consequent influence of the radium. 

 Although in all the numerous tests made, this reaction 

 was thoroughly constant and satisfactory, the glow emitted 

 was not nearly so strong or decidedly green in colour as 

 that from the variety of fluorite known as chlorophane. 



This altered form of topaz differs from zoisite in not 

 fusing to a light-coloured slag, in giving off more H-^, O in 

 matrass, in being less hard, and in not gelatinising with 

 HCl after fusion. Epidote has nearly the same composi- 

 tion as zoisite, but contains as an essential much Fe, and 

 thus affords a black slag by fusion on coal. Wollastonite 

 is easily decomposed by HCl with the separation of Si, but 

 does not form a jelly. It is also easily fusible to a glassy 

 globule ; it therefore cannot belong to this species. In 

 addition there exists a dissimilarity in both hardness and 

 specific gravity. It has a strong outward resemblance to 

 spodumene, and has been considered one of the alteration 

 products of that species. 



As tlie substance presented so many unusual characters, 

 a specimen was submitted to Mr. Robert Sticht, who gener- 

 ously had most careful analyses made, and as his report is 

 replete with scientific data of considerable mineralogical 

 interest it is herewith produced in full. Mr. Sticht 

 remarks : — 



"The results on No. 1 are as follows: — The contamina- 

 tions were knocked off, and only the clean material was 

 analysed. However, it was quite obvious that even this 

 contained an admixture of fluorite, which could not very 



