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XXXIX. 
OIN" THE OCCUEEENCE OE IDOCEASE IN THE COUOTY 
MONAGHAIS'. By Peofessor J. P. O'EEILLY, Eoyal College 
of Science, Dublin. 
[Read April 28, 1890.] 
In October of 1888 I received, from Dr. Hall, of Monaghan, a sample 
of an iron and manganese deposit which, as he informed me, occurs in 
the townland of Calliagh, county Monaghan. The specimen forwarded 
presented, along with the well-marked iron ore, what appeared to be 
a thin rib or vein of quartz, penetrated by a straw- or honey-coloured 
mineral, having a lamellar, irregularly -radiated structure, in places 
distinctly plumose, which passed into the black ferruginous portion. 
This honey-coloured mineral I determined, from its density, 3'3407, 
and its hardness, about 5, to belong to the epidote group ; and through 
the kindness of Professor Hartley, I was enabled to have it analysed 
by Mr. L. T. Spencer, then an associate student of the college. The 
results were communicated to me in June, 1889, and are as follows : — 
Silica, 40-06 
Alumina, 16-03 
Lime, , 37*46 
Eerric oxide, 4*23 
Manganous oxide, 1*16 
Cupric oxide, 0-21 
Soda, 1-00 
Loss of moisture on heating to redness, 2-07 
102-22 
The following formula was deduced from this constitution : — 
7 Si02 2 (Ee^O^, APO=^), 7 (CaO, MnO, CuO), 
or, approximatively, 
3 (CaO, MnO, CuO) (Ee^O^, APO^) 3 SiO^, 
or, generally, 
3 M ^0, M"^303^ 3 SiO^ 
