272 H. L. Wells — Bismutosphcerite from Connecticut. 



the weight in water was taken. Heated in the closed tube it 

 gives off a minute quantity of water and melts readily. It dis- 

 solves in acids with effervescence; with HC1 a small, flocculent, 

 black residue is left in which bismuth and sulphur were detected ; 

 with HN0 3 it dissolves completely. Scattered through the gray 

 material numerous minute shining scales are to be noticed, which 

 are most numerous along the cracks or more easily separated 

 surfaces. A small cavity in the specimen was lined with these 

 scaly crystals. They have a white color with a brilliant luster. 

 Their aspect is orthorhombic, but they are too small and thin for 

 measurement. Qualitative tests showed that they are composed 

 of an anhydrous bismuth carbonate, and it seems probable that 

 their composition is identical with that of the massive material 

 in which they occur, but, unfortunately, there was not enough 

 of the crystals which could be separated from the gray material 

 to afford material for a quantitative analysis. 



On some parts of the specimen a yellowish-white coating is 

 to be observed, which in places is made up of minute spherical 

 nodules, the form on a small scale of the original bismutosphaa- 

 rite.* This is also apparently an anhydrous bismuth carbonate, 

 but, like the scaly crystals, its quantity is too small for quanti- 

 tative examination. 



Mr. S. L. Penfield has kindly made an optical examination 

 of the gray substance and reports as follows: "A ttjin section 

 does not at first sight appear to be homogeneous, but shows under 

 the microscope a dark ground-mass through which irregular 

 patches of a pale yellowish-green color are scattered. The light 

 patches are not perfectly transparent, but are translucent and 

 have the appearance of a kaolinized feldspar. The material of 

 the darker ground-mass is probably the same as that of the light, 

 but stained and rendered practically opaque by fine particles of 

 dust of some black material. If, as is probable, the mineral is a 

 decomposition product, the black dust-like particles may be the 

 last traces of the original mineral. Light streaks, which may 

 be original cleavage directions along which decomposition has 

 gone on more completely, indicate crystalline structure, while 

 the lighter, translucent parts of the section polarize the light 

 and show an extinction parallel to these directions." 



A chemical examination gave much more satisfactory results 

 in regard to the purity and homogeneity of the mineral than 

 would have been expected from the results of Mr. Penfield's 

 microscopic examination. The actual amount of the black ma- 

 terial, probably bismuthinite in an extremely fine state of divis- 

 ion, which had such a marked influence upon the transparency 

 of the thin section, proved to be very small ; moreover, a careful 

 qualitative analysis showed that the only impurities besides the 

 * In this a size larger than that of a pea is mentioned by Weisbach. 



