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VI. Description of Hopeite, a New Mineral, from Altenberg 

 near Aix-la-Chapelle. By DAVID BREWSTER, LL.D. F.R.S. 

 Lond. & Sec. R. S. Edin. 



(Read June 17. 1823.; 



ABOUT the end of the year 1821, when I was engaged in the 

 examination of the Family of the Zeolites, Mr HEULAND was so 

 obliging as to send me a variety of Stilbite from a Calamine mine 

 at Altenberg near Aix-la-Chapelle. Upon comparing its optical 

 structure with that of the Stilbites, it was manifest that it had 

 no connection with this class of crystals, and that it constituted 

 a new mineral species. Upon mentioning this result to Mr 

 BROOKE, this acute mineralogist was of opinion that it was the 

 Silicate of Zinc. Mr HEULAND had been led to regard this sub- 

 stance as a Stilbite, in consequence of having re- 

 ceived it as such from Major PETERSEN ; but, par- 

 ticularly, from finding in the collection of Mr C. 

 H. TURNER, a single crystal of the same sub- 

 stance attached to Carbonate of Zinc, and bear- 

 ing the annexed figure, with an inscription in 

 the handwriting of the Abbe HAUY, stating it to 

 be a new variety of Stilbite, to which he gave the 

 name of Stilbite Duovigesimale *. 



* Attached to this figure is the following memorandum in HAUY'S handwrit- 

 ing : La position de cette figure est en rapport avec celle du noyau dans les planches 

 du Traite. 



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