/ 
350 W.F. Hillebrand—Lillingite and other Minerals. 
tite, argentite, pyrargyrite, chalcopyrite, galena, siderite, barite 
and calcite, the last three composing the gangue. Much of it 
but even in the densest portions the radiate structure is gener- 
ally distinctly discernible. ; 
tn order iscover, if possible, a clew to the crystallographic 
structure, and also to obtain material for analysis, specime 
were treated with hydrochloric acid without previous crushing, 
whereby the siderite and the arseniates of iron, cobalt and 
nickel were entirely dissolved. The ldllingite remained quite 
black on all parts where the gangue had been eaten away, but. 
surfaces of previous fracture retained their white color. The 
star-like forms were then seen to be composed of a consider- 
able number of long flattened ellipsoids, interpenetrating ata 
common center in every direction. When one of these clusters 
was broken through the star form appeared on the surface © 
fracture. The aggregates were joined together loosely, noW 
that the cementing material had been removed, though fre- 
quently in large clusters of many hundreds of all sizes, from 
those visible only with the aid of a microscope, to others an 
eighth of an inch or more in diameter. : 
A microscopic study of the finer part of the material liberated 
from its imprisonment in the gangue, and broken off from the 
larger pieces during the treatment with acid and subsequent 
washing, furnished the solution to the question as to what was 
the crystallographic form of the flattened ellipsoids composi? 
e fundamental 
is 
dome, as in fig. 1.* Frequently these two forms are equa 
developed, producing a resemblance to a low pyramid : . 
tetragonal system. Very few even of the most minute crysta sare 
the accompanying figures. with the exception of fig. 1, were ont © ee 
aid of a camera lucida. and therefore make no pretensions to crystallograpnle 
ig. 4 is magnified about 15 diameters, the others from 40 to 150 
diameters- 
