742 THOMAS LEONARD WATSON 
of a faint reddish cast which is more pronounced in the Quarry granite. 
The principal minerals in these granites are orthoclase (partly inter- 
grown with albite as microperthite), microcline, plagioclase near 
oligoclase, quartz, biotite, sphene, apatite, and zircon, with the usual 
secondary minerals which result from the partial alteration of feldspar 
and biotite. Microcline and plagioclase are present in largest 
amount. Quartz and feldspar are partly intergrown in granophyric 
structure, indicating overlapping in the periods of crystallization of 
these minerals. Carlsbad twins of the potash feldspar are noted both 
in hand specimens and under the microscope. 
Chemical analyses of these granites are given in Cols. II and V in 
the table of analyses on p. 735. The principal constituents in each 
analysis are here given for convenience of ready comparison. 
Cold Point Quarry 
Laurens County Greenwood County 
Si@eisrata eres 68.80 70.54 
vA © Panta eo eoo ae eae 15.73 14.56 
Ine Omaos neocon oe 2.14 1.06 
FiO ce a memicaecre: T57 1.62 
INI © eae esatenetnscns 1.16 0.78 
CAO i ee careers. 1.64 I.28 
INGA Oa au pieacremtranare 3-45 3.07 
KE ee staan s es 4.54 5-37 
A comparison of these analyses shows the Quarry granite to be 
slightly more acid and to contain about 2 per cent. more of total 
alkalies. In both, the percentage of K,O exceeds that of Na,O by 
a fraction more than 1 per cent., but molecularly the latter exceeds 
the former. 
The granite exposed along the road one mile south of Winnsboro 
in Fairfield County varies but slightly from the Quarry type, the 
principal difference, being the presence of additional hornblende to 
biotite in the former, which is apparent only in thin sections. As 
previously stated on p. 733, this is the only granite in the state 
studied by me in which hornblende occurs. Its principal minerals 
are orthoclase, microcline, oligoclase, quartz, biotite, hornblende, 
apatite, zircon, sphene, and the usual secondary accessory minerals. 
A part of the orthoclase is intergrown with plagioclase (albite) as 
microperthite. Of the feldspars, microcline and plagioclase are 
