ON METEORIC CHROMITES. 
By Wirt Tassin, 
Assistant Curator, Division of Mineralogy, U. S. National Museum. 
The analyses of many meteorites show small percentages of 
chromium, which is present, in part at least, combined as chromite. 
So common is the reported occurrence of this mineral in meteorites 
that it may be regarded as a constant constituent. The amount 
present is small; the stones and stony irons rarely contain as much as 
3 per cent of chromite and usually less than 1 per cent, while the 
irons generally carry less than a hundredth of a per cent. 
The small amount of chromite together with the small quantity of 
the meteorite usually available for chemical and mineralogical study 
has made it difficult in the majority of cases to do more than report 
the occurrence of the mineral, a condition that apparently makes it 
worth while to bring together the results of the several analyses of 
meteoric chromites obtained from certain of the meteorites belong- 
ing to the Museum collections. As a matter of convenience each 
chromite will be described under the name of the meteorite from 
which it was derived. 
THE MOUNT VERNON METEORITE. 
Chromite occurs quite abundantly in this pallasite in two forms— 
as minute rounded grains frequently occluded in the olivine, and as 
crystals which are to a large extent probably contained in the 
eutectic of the metallic portion. The crystals are occasionally of a 
considerable size, one of them being a millimeter in diameter. They 
are more or less perfect octahedrons, rarely modified by other forms, 
and then only by oo O (110) as noted in one instance. Color brilliant 
black with a metallic luster; nonmagnetic, specific gravity 4.49 at 
18° C., and of the following percentage compositon : 
O15 Oy ee ee See DO BAS Sei ao 65. O1 
ATS Oat sett a Sa BR nel ee et Sa ns pa tg aE AGE OD 
LENT S| ©) jerk ecto Cece ot arn RR eae papas a 18. 97 
MgO ____ 2 eee nile CAE Se Sg So Sea eae ee ae 5. 06 
PROCEEDINGS U.S. NATIONAL Museum, VOL. XXXIV—No. 1628. ee 
