Reéxamination of American Minerals. 49 
These give the formula, (Fe Mg)4 Si?—=R* Sie Si, 
Atoms, At. weight. = hong Oxygen ratio. 
Silica, 3 1731-93 3°59 8 
pies iron, 24 1125-00 3480 1} 
rm 14 375:00 11°61 
is t na chemical constitution of hornblende, and from its 
hipaa characters it was long since referred to this species. 
21. Hydrous Anthophyllite—an Asbestus. 
Thomson gave this name to an asbestiform mineral, which is 
found associated with chlorite on New York Island.* His analy- 
SiS gives: 
Bi Mg e h Al H 
5498 1338 983 120 680 1:56 1145-99-20 
We have received undoubted specimens of this mineral from 
Messrs, Vaux, of Philadelphia, and Silas R. Horton, of New 
ork, The ‘asbestiform mineral, carefully freed from the chlo- 
rite and other impurities, gave on two analyses: 
1. 2. 
Silica, F ‘ 58:20 ; ‘ 58-47 
Magnesia, ‘ 28°96 : 29°71 
Protoxyd iron, : 8°46 : : 9°06 
Soda, . 83 ‘ ‘ ; 
Potash, ; é trace : ; trace 
Ignition, : ‘ 2°26 : 
Alumina, ‘ ; trace : : trace 
98°76 100°38 
These correspond to the formula, R¢ Si or R* Si2-++R Si. 
At pies At. weight. Per cant Oxygen ratio, 
Silica, 1732-00 sae 
Magnesia, A 87500 30°90 1 
Protoxyd iron, 225°00 794 $ 
This is the formula given for the last mineral, and the compo- 
sition is that of an asbestus or magnesian hornblende. 
22. Monrolite, identical with Kyanite. 
S mineral was described by Professor Silliman, Jr.t as a 
So silicate of alumina resembling Weerthite. Prof. Silliman, 
OWever, observes that the water varied in ‘several specimens ex- 
amined from 3-09 to 1:84 per cent. ; subsequent examinations} 
made by one ee us showed that the water in the pure mineral was 
not over one t 
In the aint ya recently made, we find that the silica and alu- 
mina are the same as in kyanite, and that the high silica obtamed 
by the analyst quoted, was undoubtedly owing to the impurity 
of the mineral, as a careful examination with the magnifier shows 
Plates of quartz eget with almost every specimen. ee 
* Thomson's Mineralogy, + This Journal, [2} viii, 88 
$¢ Dana’s Miwedacs: Fs cit hae 
Skvonp Szniss, Vol. XVI, No. s la 1863. oes 
