Eakle and Muthman—So-called Schneebergite. 245 
Some difficulty was experienced in isolating the material for 
an analysis and extreme care was necessary in order to get a 
perfectly pure product. The separated particles of ore fell 
easily by weak pressure with an agate spatula into single iso- 
tropic crystalline grains ; a microscopical examination of this 
coarse powder showed an accompanying mixture of magnetite, 
zincblende, irregular fragments of milk-white quartz, calcite 
and almost opaque, unknown black particles of a mineral 
which was unattacked by acids, apparently some silicate; all 
of these impurities were present only in very small amounts 
and made at most 5 per cent of the total weight. The material 
was first digested with dilute hydrochloric acid and afterwards 
nitric acid was added and, after a short time, warmed in order 
to be sure of the decomposition of any sulphide present ; the 
granular crystals of schneebergite are not attacked if the acid is 
sufficiently dilute. The well-washed and dried residue still 
contained quartz and the black particles, but these were 
removed mechanically and about 0-4 gr. of the mineral was 
obtained, which in respect to purity was all that could be 
desired. : 
The specific gravity was first carefully determined by means 
of a pycnometer; the amount of substance used was 0:4110 
gr, and the specific gravity found was 3°838 (the average of 
three weighings from 3°823-3°848). Weidel found with 0°17 
gr. the gravities 3°9, 4:1 and 4:3. As the amount of mineral 
was so small, a qualitative analysis was conducted in a quanti- 
tative way according to Weidel’s results, who, as above stated, 
found antimony and calcium as the principal elements. The 
material was fused with potassium and sodium carbonates, 
with the addition of some nitric acid (in order to prevent the 
reduction of the antimony); the fused mass was dissolved in 
hydrochloric acid and there resulted a liquid, colored yellow by 
the iron present, which contained a substance having the exact 
appearance of silica. On the addition of hydrogen sulphide 
a deep brown precipitate was formed, which showed when 
examined, besides much sulphur from the oxidation of the 
hydrogen sulphide by the salts of iron, nothing but silica and 
some platinum, which last evidently came from the fusing- 
erucible, as fusions containing saltpeter will always attack 
latinum somewhat. Neither antimony, bismuth nor copper, 
which Weidel found, were present. 
Further analysis of the filtrate gave only iron and calcium 
and the amounts were Fe,O, 32°33 per cent and CaO 32°58 
per cent. An exact determination of the silica could not be 
made because it was partly used in the qualitative analysis of 
the precipitate. Professor Groth kindly placed at our dis- 
posal more of the material from the museum collection and 
