oie ee he 
XV.—ON STILBITE FROM VEINS IN METAMORPHIC 
(GNEISS) ROCKS IN WESTERN BENGAL, sy V. BALL, 
M.A., F.G.8S., OF THE GEOLOGICAL SuRVEY oF INpIA. 
[Read November 18, 1878. ] 
THE occurrence of stilbite in metamorphic rocks, though by no 
means a new discovery, is still of sufficient rarity to be worthy 
of record. To the best of my belief there is no published account 
of this mineral: having been previously found in this association 
in India; and so far as I have been able to ascertain, it has not very 
often been met with under similar circumstances either in Europe 
or America. Imay mention that during the recent meeting of the 
British Association several of the mineralogists to whom I showed 
the specimens seemed to regard the discovery as being one of 
interest, and without a parallel in their own personal experience. 
The Cretaceous Basalts of India, otherwise known as the Dekan 
trap, include, in certain places, remarkably fine crystals and 
erystalline masses of various zeolites—including stilbite ; but the 
mineral about to be described, though possibly of secondary, if 
not of intrusive origin, does not occur in contact with any demon- 
strably voleanic materials. It was found in the vicinity of a small 
coal-field*—one of a series of basins of coal measures which I 
surveyed in the early part of the present year. Three distinct 
veins of the mineral were observed. The principal one is from 
half an inch to ten inches wide, with a vertical underlie and 
strike of about 20° North of West to 20° South of East. Though 
for the most part the vein lies parallel to the planes of foliation 
of the pink porphyritic gneiss which encloses it, it does not 
invariably do so, as it cuts across them obliquely at several points. 
A second vein close by, is in places one foot wide, but thins out 
to nothing within a short distance. A third vein of inconsiderable 
dimensions was also discovered. Leys regularly in reference to 
* The precise locality where it was found may be thus indicated. It is just inside the 
mouth of a stream from the Bijka peak which joins the Atee river, south of the village of 
Manjuri, about 16 miles 8.W. of Daltonganj, in the Palamow Subdivision (vide Mem. 
Geol. Surv., India, Vol. xv., p. 37.) 
Scien. Proc. R.D.S., Vou. u., Pr. 1. K 
