18 HAYDEN : GEOLOGY OF THE PROVINCES OF TSANG AND 0. 
consist chiefly of garnetiferous mica schist, which is frequently found in 
contact with the gneiss and granite ; less common are scapolite- 
granuliteSj crystalline limestone, quartzite and graphitic gneiss. 
On the road from Gangtok to Tangu, crystalline limestone was 
observed at three localities, viz. : — 
(1) on the right bank of the Tista, at about i \ miles above the 
Tung bridge, and thence at intervals up to Tsiintang ; 
(2) on the left bank of the Lachen river, at about 3 miles 
above Tsiintang ; 
(3) on the left bank of the Lachen, near Pangri, half-way 
between Lamteng and Tallum Samdong. 
The first outcrop of limestone seen above Tung is a vertical bed 
about 30 feet thick and consists of a whitish and pale-grey banded 
rock which, if polished, should afford a handsome ornamental 
stone. 
The limestone above Tsiintang, and that near Pangri, is a white 
crystalline rock composed of calcite and dolomite in approxi- 
mately equal proportions, with various accessory minerals which 
include scapolite, diopside, chondrodite, spinel, sphene and, in some 
instances, quartz, felspar and actinolite. Near Tsiintang, the lime- 
stone is associated with the quartzite recorded on Professor 
Garwood's map, and with an interesting series of pyroxene-scapolite 
granulites, and at Pangri it appears to be connected with a graphitic 
biotile-garnet-sillimanite gneiss. With the exception of the quartzite. 
none of these rocks are mentioned by Professor Garwood, but he 
describes two interesting rocks, to which he ascribes a sedimentary 
origin, from the western face of Pandim. One of these is composed 
chiefly of garnet, epidote and hornblende, but contains also quartz, 
scapolite, calcite and augite, and is thus probably genetically related 
to the scapolite granulites of Tsiintang. 
Owing to the highly complicated nature of the tectonic conditions 
prevailing in this area and the density of the vegetation covering the 
mountain sides, it was impossible to ascertain, during a rapid 
traverse, the mutual relations of the several members of this crystalline 
{ 139 ) 
