S. L. Penfield — Connellite from Cornwall. 83 



The mineral is one of special interest to the author owing to 

 its apparently close relation to the newly described Spangolite,* 

 as well as the general interest which one always has for such a 

 rare and beautiful mineral, which has been for so many years 

 mentioned and partially described in mineralogical literature. 

 Fortunately Prof. Brush had in his cabinet a specimen of the 

 mineral, labeled Camborne in Cornwall, which he had obtained 

 from the Mineralien-Niederlage in Freiberg and which he gen- 

 erously placed at my disposal. The specimen was composed 

 chiefly of octahedral cuprite, in the cavities of which the con- 

 nellite had deposited, mostly in radiated groups ; malachite and 

 agate were also associated with it. It did not at first seem pos- 

 sible that enough material could be obtained for making an 

 investigation, but on breaking into the specimen additional 

 cavities were found which contained crystals. Owing to the 

 beautiful blue color of the mineral it could readily be distin- 

 guished from the cuprite, and by careful selecting nearly 0*05 

 gram was obtained on which not the least trace of impurity 

 could be detected when examined with a strong magnifying glass. 

 The specific gravity of two of the pieces was taken in the barium- 

 mercuric iodide solution, and found to be 3*364:. There was, 

 therefore, the possibility of obtaining still more of the mineral 

 hy crushing and sifting all of the material which had been 

 picked over and separating by means of the heavy solution. 

 The separation presented some difficulties, as the cuprite was 

 somewhat attacked by the heavy solution, and the malachite 

 varied in specific gravity (owing probably to impurities), some 

 of it being almost exactly like the connellite ; the mineral was, 

 however, separated from the heavier cuprite and lighter agate, 

 "but still contained malachite, from which it was further sepa- 

 rated by hand picking. The powder was repeatedly brushed 

 from one watch glass to another and examined in a strong light 

 with a lens, so that every bit of malachite which might perhaps 

 be attached to the connellite might be seen and removed. This 

 repeated examination of the powder assured the author that 

 the material which he had for examination was of exceptional 

 purity. Altogether 0*074 gram of the pure material was ob- 

 tained. Before commencing the chemical analysis the crystals 

 were carefully examined. The habit agrees well with the gen- 

 eral description of Maskelyne ; most of the crystals are slen- 

 der prismatic, terminated by a pyramid of the opposite order. 

 Crystals are seldom over 0*15 mm in diameter, the largest are in 

 slightly divergent groups, and it was not only difficult to iso- 

 late a single terminated individual, but also to adjust it on the 

 goniometer. In three cases the adjustment was made so that 

 the terminal angle of the pyramid (1011 /\ 0111) could be 



* This Journal, III, xxxix, 37 0. 



