48 CONTRIBUTIONS TO MINERALOGY. [bull. 262. 
of bluish-green color on "copper-pitch ore." The latter is isotropic 
and undoubtedly a distinct mineral from the chrysocolla, of brown 
color in varying tints, some of it opaque and showing evidence of 
concentric deposition. On top of the chrysocolla are thin crusts of 
quartz and some calcite. The chrysocolla has three different struc- 
tural forms, as seen under the miscroscope: (1) The dominant mass il 
a cryptocrystalline to microcrystalline aggregate of particles with 
high birefracting index; (2) very fibrous and felted aggregates of 
same substance giving undulatory effects between crossed nicols :md 
medium high colors; (3) fibrous crusts on top of 1, or also in thin lay- 
ers between masses of 1, the individuals having such a remarkably 
parallel orientation that the aggregate of them appears almost like 
single. crystals between crossed nicols, with black shadows sweeping, 
across them when the table is turned. The extinction is parallel to 
the fibers, double refraction strong, about like augite, character nega- 
tive. The same optical characteristics were repeatedly observed im 
thin sections of chrysocolla from Metcalf and other places. Reniform 
deposits were sometimes noted, the center of cryptocrystalline material 
coated with coarsely fibrous and highly birefringent material. 
Sections from the Coronado and Metcalf mines often showed pseudo- 
morphs of pyrite consisting of a shell of limonite with kernel of fibrous 
chrysocolla. 
The observations of Jannettaz a on chrysocolla from Boleo, Bajs 
California, Mexico, led to the same results as described above, bul 
seem generally to have been overlooked by editors of text-books. 
COPPER-PITCH ORE. 
Under this old German name is described a dark brown to blacl 
substance, sometimes dull but generally with glassy to resinous luster 
hardness about 4; streak dark brown. It occurs among the product 
of oxidation of the deposits in limestone, as at the Detroit and Long 
fellow mines and Modoc open cut at Morenci, and is associated wit 
azurite, malachite, and chrysocolla, often inclosing these minerals o 
replacing in branching veinlets, together with azurite, a shale-lik 
mass, probably largety composed of kaolin. In thin section it is some ■ 
times opaque, but often also translucent, gradual transitions obtainin ;j 
in the same section, and occurs in irregular or concretionary masse; j 
often containing small embedded crystals of a doubtful mineral, poi 
sibly a silicate of zinc. Between crossed nicols the translucent miner} I; 
always proves entirely isotropic and, except for varying depth of cole ij 
and the small crystals mentioned, entirely homogeneous. 
« Bull. Soe. Min., Paris, vol. 9, 1880, p. 211. 
