Samuel Lewis Penfield. 357 



quality. Botli in the importance of the problems treated and 

 in the ability and technical skill with which they are handled 

 his work is of the very highest scientific character, and the 

 greater part of it, together with his methods and ideas, has 

 already become classic in the history of his science. In regard 

 to this the following facts are of interest and may be men- 

 tioned. Fourteen new mineral species were established and 

 described by him, — sometimes in combination with others. 

 These are : Bixbyite, Canfieldite, Clinohedrite, Gerhardtite, 

 Glaucochroite, Grqftonite, Ilamlinite, IlancocJcite, Leuco- 

 phoenicite, Nasonite, JSfesquehonite, Pearceite, Poeblingite, 

 Spawgolite. 



What in reality was of even greater importance was the 

 large number of already described minerals, many of them 

 well known and prominent species, which he studied and whose 

 true chemical composition and mineralogical affinities he estab- 

 lished. These include Alurgite, Amblygonite, Argyrodite, 

 Auriekalcite, Childrenite, Chondrodite, ClinoliumUe, Con- 

 nellite, Cookeite, Ganomalite, JETanlcsite, Herderite, Howlite, 

 JZumite, Monazite, Palstonite, Staurolite, Sulphohalite, 

 Topaz, Tourmaline and Turquois. 



Among the more important facts which he brought out as 

 the result of his chemical work was the discovery of ger- 

 manium in silver ores from Bolivia and the determination of 

 the correct formula and crystallization of argyrodite, the Frei- 

 berg mineral in which germanium was originally discovered. 

 Another contribution of the highest value was his recognition 

 that fluorine and hydroxyl are isomorphous in chemical struc- 

 tures, and that they play a significant function in the com- 

 position of many minerals whose correct formulas may be 

 derived by the application of this principle. He showed also 

 that the variations in the physical properties of certain promi- 

 nent minerals were dependent upon the variations in the rela- 

 tive amounts of these radicals. This was shown very strik- 

 ingly to be the case with topaz, and applying these ideas to the 

 chondrodite group of minerals, whose relations until then had 

 proved an unsolved problem, he derived their correct com- 

 positions and showed that they formed a definite series with 

 related physical properties. He was, moreover, able to indi- 



