252 C. Palache — Mineralogical Notes. 



Dana* as found by liim on zoisite from Ducktown, Tenn. but 

 not supported by measurements and therefore excluded from 

 recent lists of forms. 



The form y (221) is well developed on several crystals with 

 good faces and is much the best established of the new forms. 



On nearly every crystal the edges between brachypinacoid 

 and terminal planes are replaced by groups of very steep 

 pyramidal faces which are sometimes curved and reentrant, 

 again plane and smooth, affording good reflections. The meas- 

 ured angles indicate forms of large and complex indices and 

 the variation in position is so considerable in different crystals 

 that they can only be regarded as vicinal forms. Some of the 

 measurements made upon them are however presented in the 

 table since they are very characteristic for the locality. 



The axial ratio calculated from the measurements of thirteen 

 good faces on a single crystal coincides almost exactly with the 

 value calculated by Tschermak for zoisite from Ducktown, 

 Tenn. 



a : b : c 

 Tschermak, Ducktown 0-6196 : 1 : 0.3429 

 Palache, Chester 0-6191 : 1 : 0-3429 



2. Phenaoite as an Alteration Product of Danalite from 

 Gloucester, Mass. 



In 1903 an abundance of danalite in small grains and masses 

 up to 8 cra diameter was found in a small ballast quarry opened 

 in granite on the line of the railway, about half way between 

 Gloucester and Rockport, Mass. On some of the larger masses 

 of pale to dark pink danalite can be seen faint indications of 

 octahedral planes. Most of them are quite irregular and much 

 fissured, showing the beginnings of decomposition, and in one 

 case the greater portion of such a mass has undergone com- 

 plete alteration, the resulting products showing that all the 

 essential constituents of the danalite were retained in the 

 cavity. 



It will be remembered that danalite is a silicate of beryllium 

 iron, manganese and zinc, containing sulphur. The decompo- 

 sition products found in this cavity comprise phenacite, spha- 

 lerite, pyrite, manganiferous siderite, hematite, quartz, chlorite, 

 albite and kaolin. The fragmentary condition of the cavity 

 when found made it impossible to attempt a quantitative esti- 

 mate of the proportion of the original chemical constituents 

 preserved in this aggregate. But it is evident that in a quali- 

 tative sense phenacite represents the beryllium content of the 

 danalite, sphalerite and pyrite the sulphur, zinc and part of the 



*Dana, J. D., Mineralogy, 1877, 290. 



