Chap. IX. ] associated non-manganiferous minerals. 221 
softness be not tested it is liable to be mistaken for felspar in the hand- 
specimen, on account of its pearly lustre on cleavage faces. Under the 
microscope it may be mistaken for apatite if its high refractive index 
combined with its low double refraction be noticed ; whilst if one is 
hurriedly examining a series of rocks, and does not notice the high 
index of refraction of the mineral, it may be mistaken for a felspar. The 
localities at which it has been found as a constituent of rocks of the 
gondite series are Ghoti, Chargaon, and Kailidongri At Kajlidongri 
this mineral also forms one constituent of a vein traversing the man- 
ganese-ore deposit ; the other constituents are quartz, the arsenate 
mentioned on page 219, a black ore, probably braunite, and a 
small amount of plagioclase felspar. In this vein the barytes indivi- 
duals may be as much as 2 or 3 inches long. Except for the presence 
of the manganese-ore and the arsenate, the rock is not unlike the 
quartz-ba-ytes veins described by Dr. Holland from the Salem district. 1 
These veins are considered to be of pegmatitic origin r.nd to have 
solidified from an injected mobile magma. From the mode of occurrence 
of the Kajlidongri vein it would be mipossible to decide whether it be 
an ordinary mineral vein or also of pegmatitic origin ; but the presence 
of plagioclase in the rock rentiers it improbable that it is an ordinary 
mineral vein. The arsenate, moreover, may be regarded as taking the 
place of the apatite so often found in pegmatites, and consequently we 
can regard the Kajlidongri rock as possibly the product of the solidification 
of an injected magma. The manganese-ore that it contains may easily 
have been absorbed by the magma from the inanganese-ore deposit at 
the time of its intrusion. 
1 Hcc. G. 8. I.. XXX p. 236, ( 1807). 
