20 Dr. Genth’s Contributions to Mineralogy. 
11. Garnet. 
From Yonkers, N. Y.—This beautiful massive red garnet, 
which I have found in many collections labelled ‘‘ Pyrope,” has 
been examined in my laboratory, by Mr. Wm. J. Taylor. 
B.B. it fuses to an iron black, shght'y magnetic globule ; with 
borax it gives the reactions of iron, and with carbonate of soda - 
those of manganese. It is acted ite by hydrochloric acid, but 
= completely decomposed. ‘The analysis gave the following 
sults. 
mee y 38°32 per cent. contains Oxygen 19:90 ie 
Alu ‘49 = “4 10°05 = 1 
aed a of iron (FeO) 30°23 s « bee 
Oxyd of anese, 2°46 - : 1016 = 1 
= gaia 6:29 “ * 2 31 3 
. 1:38 fs 0°39 J 
b. Bab Grebuas Creek, Delaware county, Pa.—Under the 
head “ Pyrope,” Prof. Dana mentions this beautiful gem, stating 
his doubts, that it belongs to this species. The followin analy- 
sis, ome by Mr. Chs. A. Kurlbaum will, show the correctness of 
his vie 
B.B. 7 behaves like a; its composition is: 
eens . 40°15 per cent. contains Oxygen, 20°86 Sa 
TT “ 7 “ 9°71 = : 
od of 3 iron (FeO) 26°66 : . 5°92 
Oxyd of Manganese, 185 . . 0°42 mee 
ioe Ue aes megosels, viggg PARE =e 
Lime, * . 1:83 : f 052 |} 
12. Allanite. 
Though we have already numerous analyses of this mineral, 
we are not yet arrived to a certainty with regard to its composi- 
tion. This is owing to various causes, principally, I suppose, to the 
fact that analysts have in most cases not taken the necessary care 
to ascertain, whether the iron in allanites is in the form of oxyd 
(FeO) or in that of sesquioxyd (F'2Q:), or in both states of oxyd- 
ation. At my request, Mr. Peter Keyser made a series of analy- 
ses of American allanites. The separation of the oxyds of ce- 
rium, lanthanum and didymium from iron and alumina in all the 
analyses («) was made by sulphate of potash; in analyses (@) by 
oxalic acid; sesquioxyd of cerium was separated from lanthana 
and oxyd of didymium by very diluted nitric acid and the oxyd 
of iron by chlorid of gold and sodinm. All the rest of the de- 
terminations were made i in the usual manner. 
a. Allanite from gn county, N. Y.*—Massive, Apclenvage 
could be be detected ; H. 5:5; Sp. gt. (at 17° Cels.) =3-782 ; lustre 
— ome seri my note in the Am. Journ. of Sé, 28 
é 
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