58 ; REPORT—1863. 
Hornblende of Donegal Granitic Syenite. 
1 TG? gee hol aa A i a Aa 47:25 
2. STE eae ce ea a leis MORALE ac 5°65 
run permempye. oe... te eee 19°11 
remo r e  ss spi oy See Ley 
MBE BOUIN Oe Ses sak ss oa ee 11°26 
MAGE. Soke ner se tee ses eee 0-98 
Potash yr. ccstoebis ate o Rites ik eke 1:04 
Tron (pretomide os iitsicas vase des 0-94 
Manganese (protoxide) ...,....,. ingame bio 
99°69 
B. Accidental Minerals. 
1. Sphene.—This mineral is very like the clove-brown sphene of Norway : 
it is found in the granite, when the latter becomes basic, containing much 
black mica and oligoclase; but it is principally found in a rock formed of a 
paste of quartz and feldspar, that often lies between the granite and limestone 
of the metamorphic rocks of Donegal. This is especially observable at An- 
nagary and Barnesbeg, where this rock is so abundant as to become entitled 
to the name of sphene-rock; and it cannot be distinguished from similar 
rocks from Norway. 
2. Schorl—This mineral accompanies orthoclase in veins, and is often 
curved and cracked, showing the wider openings of the fissures next the 
convex side, and filled with quartz, as if the curvature of the schorl and the 
filling of its fissures with quartz were the result of an action that took place 
after the deposition of the mineral. 
3. Beryl.—The only known locality for beryl in Donegal is Sheskina- 
roan, near Dunglow. It is green, with occasionally a shade of blue, and 
occurs both in reefs of quartz traversing the granite along its leading joints 
and also in the granite itself, which, in this case, becomes very quartzose, and 
its black mica disappears, giving place to fine rhombs of margarodite. 
The beryl of Donegal has neyer, so far as we know, been analyzed—a cir- 
cumstance which may give some additional value to the following analysis :— 
Beryl, from Sheskina-roan, Co, Donegal. Sp. gr.=2-686. 
Babe ee Se Oe Wn ike 65:52 
Alumina ..... A): Sls. Geer ha 17°22 
pgs... 4.5. MH Ross «lye sas Vee 13:74 
Ayan BPA EN A hoists Moma teyrteion 1:53 
Dee GGL. 3.2). NERO Ricks: dco ncetehe 0:43 
BCT cTe TE te Gan ce ee et 0-13 
Gh 2) eae te eee ame? ear ;. » 0:80 
99-47 
4. Garnet.—This mineral, in bright ruby-coloured crystals, is found in the 
granite of Glenties, Annagary, and other localities. Form dodecahedral. 
' 5. Molybdenite and Copper-pyrites——These minerals are found in yeins of 
apis. Garvary Wood, near Castlecaldwell, associated with oligoclase and 
ack mica. 
Minerals occurring in the Non-granitic Rocks of Donegal. 
By reference to the Appendix to this Report, it will be seen that the minerals 
which have been hitherto observed in the county are about sixty in number, 
