1098 General Notes. [ November, 
each edge replaced by a reéntrant angle. A microscopic exam- 
ination of thin sections of these crystals shows that they are 
divided into four secants with a faint irregular action on polarized 
light. Very many crystals show a perfect but small trisocta- 
hedron in their center, around which the exterior portion appears 
to be a secondary growth. 
Mr. J. P. Iddings! of the U. S. Geological Survey communi- 
cates a very interesting account of minute fayalite crystals which 
occur in the lithophyses of the obsidian and rhyolite in the Yel- 
lowstone Park. They are less than 2™™ in length, black in 
color and tabular in habit. The following forms were deter- 
mined by Mr: Penfield: PS; 6 PS; 3 P2, P, Po and ae 
An analysis by Dr. Gooch gave: 
SiO FeO . MgO 
32.41 65.49 i 2.10 
Fayalite has heretofore been known only on artificial slags to 
which the obsidians of the Yellowstone have a close resemblance. 
Messrs. Cross and Iddings? describe the wide-spread distri- 
bution of the mineral allanite as a rock constituent. The chem- 
ical nature of this mineral was determined by an analysis by 
Hillebrand of material isolated from a biotite porphyrite of the 
en Mile District, Colorado. Crystals of an exactly similar 
nature were discovered in thin sections of all the more acid va- 
rieties of massive rocks from many widely separated localities. 
Mr. W. G. Brown? gives an account of a quartz-twin found- 
in the soil of Albermarle Co., Va., which closely resembles those 
long since described by G. Rose from Reichenstein in Silesia. 
The twinning-plane is, however, regarded by Mr. Brown notas R, 
but as —56R, as suggested by Naumann. The same writer 
describes the occurrence and crystallography of the cassiterite 
from Irish creek, Rockbridge Co., Va. i 
Mr. Geo. F. Kunz’ describes the native antimony and its as- 
sociations at Prince William, York Co., New Brunswick. The 
antimony most commonly occurs in rounded or elongated mas- 
ses having a compact, finely granular texture. More remark = 
however, are coarsely crystalline radiating masses consisting © 
blades four inches in length and one-eighth of-an inch in width. 
Stibnite and kermesite are the only antimony minerals thus far } 
observed associated with the native metal, although others doubt- 
less occur. ee 
2 Ib., Aug., 1885, p. 1 
 * Tb., Sept., 1885, p. ror. 
An 
1 Amer. Jour. of Science, July, 1885, p. 58. 
08, 
* Amer. Chem. Jour., Vol. v1, No. 3. 
Amer. Jour. of Science, Oct., 1885, p. 275. 
