554 A. E. V. Zealley — Calc- Silicate Limestones, Donegal. 



85-80 

 11-48 



>l 



Class I Persalane. 



85-80 \ 7 

 /I 



. . . . Sub-class I . . ■ . Persalane. 



Q, _ 51-30 / 5 \ 3 



"jT ~ ■u-5o\'3^/'5' • • • • Order Columbare. 



— ^ — ^r~7^ — ^ ^ ,■ — \ — y — .... Ean": Alkalicalcic. 



CaO 46 \ 3 / 5 " 



Name of Rang — Kiesenase.i 



KoO 18 / 3 \ 1 „ . ^ ,. 



Name of Sul-rang — X. 



The American authors suggest no name for this Sub-rang, since no 

 rock of importance known to them seems to come here, though they 

 are aware of analyses of rocks which would fill the blank. The 

 Orange Grove Granite appears to be of sufficient importance to 

 warrant us in assigning the name of Orangose to the sub-rang. 



Eather significant, and showing to some extent the value of the 

 system, is the fact that a similar rock from the Transvaal with 

 minerals in similar proportions, with the exception of a large per- 

 centage of the basic constituents, is described by the American 

 writers as Vaalose} 



DESCRIPTION OF PLATE SXVII. 



Fig. 1. Biotite, with pleochroic haloes, associated with yellow epidote. Small 

 flakes of green mica in the turbid plagioclase to the right. To the left, 

 near the base, is a large hexagonal section of an apatite crystal. 

 Power, ^". Ordinary light. 



,, 2. Large reddish-brown crystal of sphene, showing its unusually deep colour 

 and elongated form. The turbid felspars contain unaltered patches, 

 together with small grains of epidote and flakes of mica. Chloritic patches 

 are shown. Power, |". Ordinary light. 



,, 3. Turbid crystal of plagioclase, with clear secondary felspar in optical con- 

 tinuity. Microcline and micrographic intergrowth of quartz and felspar 

 are shown. Sericite is shown in its usual form of development. 

 Power, V . Crossed nicols. 



VIII. — Calc- Silicate Limestones of Donegal. 



By Arthur E. V. Zealley, A.R.C.S. (Geologist and Curator of the Rhodesia 



Museum). 



DURING the summer of 1908 I examined in the field the contact 

 metamorphosed limestones of the county Donegal, my attention 

 being mainly confined to those masses of limestone occurring as 

 xenoliths in the granite. These strongly metamorphosed limestones 

 frequently contain the interesting rock named by Dr. R. H. Scott 

 ' Sphene-rock ', which (" Granitic Rocks of Donegal " : Journal of the 



' ' ' Alkalicalcic Rang of Columbare, the quarfelic order of Persalane, Class I, 

 from the Granites of the Riesengebirge. Silesia": Milch. Neu. Jb., 1899, 

 B. Bd. xii, pp. 152-222. 



^ "Dosodic Sub-rang of Vaalose, the Alkalicalcic Rang of Vaalare, the quardofelic 

 order of Salfemane, Class III, Cohen" : Neu. Jb., 1887, B. Bd. v, pp. 233-47. 



