1897.] Mineralogy and Crystallography. 603 
On the Zonal Structure of Crystals.—Pelikan® discusses the 
peculiarities of augite, barite, cassiterite, calcite, tourmaline and fluor- 
ite as regards their growth in zones. Of these, the first two are espe- 
cially interesting. The literature on the hour-glass and zonal structure 
of augite is reviewed, after which are given the results of work on the 
well-known “hourglass” augites of Nordmark. This structure has 
been shown to be due to the varying conditions of deposition on the 
various faces of a growing crystal. That portion of the augite sub- 
stance which was deposited on the orthopinacoid is found to be darker 
in color and to have a larger angle between ¢ and c than the material 
which grew on the base or orthodome. In the darker portions this 
angle is greater for violet than for red rays, while in the lighter parts 
the reverse is true. Etched figures show a hemihedral symmetry for 
some pyroxenes, thus confirming observations that have been made, in 
rare cases, on the crystal form. In barite the crystal faces show a 
selective force, so that hematite and cinnabar, for instance, are found 
chiefly on the macrodome (101). So far as known, there are always 
other than isomorphous molecules present in those cases where differ- 
ent substances are deposited on different face. 
After classifying the various causes of zonal distribution of color in 
crystals, the conclusion is drawn that hourglass structure is never 
caused by an intermixture of isomorphous substance, but by the pres- 
ence of some differently crystallizing er matter, or by a “ dilute 
color.” 
Miscellaneous Notes.—With the close of the year 1896, came 
the last brochures of the second volume of Hinze’s Handbuch der 
Mineralogie, already referred to in the NaturA.ist, Vol. XXV, 1891, 
p. 577. This second volume (the first has not yet been published) 
treats only the silicates, devoting more than 1800 pages to the discus- 
sion of these minerals alone. It is by far the most complete, as well as 
the most recent, work of its kind. The appearance of the first volume 
will be looked for with much anticipation by mineralogists. It is pub- 
lished by Veit & Co., Leipzig. 
A. P. Brown’ finds, on some unprecedentedly fine molybdenite 
crystals from Frankford, Pa., the axial ratio a: c—=1:1.908. The faces 
observed are: ¢ (0001, °P), o (1011, P), p (2021, 2P), q (3081, 3P), 
and m (1010, œ P). The angle c: p=77° 13’. The pyramid p (2021) 
* Tschermak’s Min. Pet. Mitth., XVI, pp. 1-64, 1896. 
* Proc. Acad. Nat. Sci. Philadelphia, 1896, pp. 210-211. 
