4:\2 Hess and Wells — Occurrence of Striiverite. 



Art. XXXVI. — An Occurrence of Striiverite ;* by Frank 

 L. Hess and Roger C. Wells. 



The mineral described in this paper belongs to the tetragonal 

 system, crystallizes like rntile and contains titanium, tantalum, 

 columbium, iron and tin. It is apparently a new mineral and 

 at one time we contemplated giving it a specific name in order 

 to differentiate it from ilmenorutile and suggest its chemical 

 composition, but this was not done for reasons which will be 

 noted. In accordance with modern views, the mineral may 

 probably be regarded as a new member of an isoinorphous 

 series of minerals crystallizing like rutile and containing some 

 or all of the metals named. 



In 1908 Prior and Zambonini described a mineral from Cra- 

 veggia, Northern Piedmont, which differs from ilmenorutile 

 in possessing a little more tantalum, in relation to columbium, 

 than had been found in any ilmenorutile up to that time.f 

 After noting its crystallographic similarity to ilmenorutile and 

 the possibility of considering it a solid solution of mossite and 

 tapiolite in rutile, Prior says: "We propose to reserve the 

 name striiverite for those members of the series rich in tantalic 

 acid and to keep the name ilmenorutile for those, like the Nor- 

 wegian specimens, in which niobic is the prevailing acid." 

 Since the name ilmenorutile is reserved "for those minerals in 

 which niobic is the prevailing acid," a fair inference would lead 

 one to suppose that their mineral carried a preponderance of 

 tantalum oxide, but as analyzed by Prior it showed Ta 2 O s and 

 CbjOj, only " in about equal amounts," — 23 # 5 per cent of each,— 

 so that the columbium oxide is in molecular excess as 88:53. 

 It is evident that their definition of striiverite does not fit 

 their mineral, although their mineral suggests the possibility 

 of others having more tantalum. In other words, they named 

 a mineral which was yet to be found. 



The mineral described in this paper carries 35*7 per cent 

 Ta 2 5 and 6*4 per cent Cb 2 B and would seem to deserve a 

 new name, but as it has been covered by the definition of 

 striiverite we shall defer to that name in order to avoid over- 

 burdening the literature of mineralogy. At the same time we 

 hope that the custom of proposing names for unknown extra- 

 polated members of a mineral series will not become general. 



* Published by permission of the Director of the United States Geological 

 Survey. 



■)• On Striiverite and its Relation to Ilmenorutile. Mineralogical Mag. , xv, 

 78-89, 1908. 



