Vol. 59.] THE TIKEE AND IONA MARBLES. 91 



11. Observations on the Tiree Marble, with Notes on others from 

 Iona. By Ananda K. Coomaraswamy, Esq., B.Sc, F.L.S., 

 F.G.S. (Bead December 17th, 1902.) 



[Plates VI & VII.] 



Contents. 



Page 



I. Introduction 91 



II. General Description 93 



III. Contact-Phenomena 9b' 



IV. Dynamic Phenomena 97 



V. Notes on the Minerals 98 



VI. Iona 101 



VII. Summary and Conclusions 102 



I. Introduction. 



Although so well known, and represented in many mineralogical 

 collections, the Tiree Marble has never been described in detail. 

 Macculloch 1 says that the Tiree flesh-coloured marble 



' resembles the greater number of the primary limestones found in gneiss and 

 mica-slate, and may be considered as a large nodule . . . The nodule of lime- 

 stone . . . appears to be an irregular mass of about 100 feet in diameter, and is 

 surrounded on all sides by gneiss.' [The marble] ' occasionally contains 

 imbedded lumps of granite or gneiss, similar to those which occur in the 

 limestone of Grlen Tilt. These are always visible at the surface, from their 

 superior power of resisting the action of the atmosphere.' 



He also describes the exposures of limestone in a field south-east 

 of Balephetrish Hill. He says that 



1 it is possible that the masses of limestone thus found in gneiss have once 

 been stratified, and that they have suffered some posterior changes by which 

 the appearances of this disposition have been obliterated.' 



Prof. Bonney 2 has given a valuable description of the dynamic 

 phenomena so well illustrated in thin sections of the Tiree Marble. 



Prof. Cole & Prof. Sollas 3 have suggested that the Tiree Marble 

 may originally have been a wind-blown coral-sand rock, with 

 abundant rounded crystals of cletrital augite, etc., such as was 

 found on the east side of Mer, one of the Murray Islands. This 

 theory appears untenable ; for it is impossible to imagine a volcanic 

 origin for the majority of the accessory minerals, which, with the 

 exception of felspar, are, on the contrary, the typical accessory and 

 contact-minerals associated with crystalline limestones in all parts 

 of the world. 



This paper embodies observations made by me in the summer 

 of the present year (1902). 



1 ' Western Islands of Scotland ' vol. i (1819) pp. 48 & 49. 



2 'The Effects of Pressure on Crystalline Limestones' Geol. Mag. 1889, 

 p. 483. 



3 ' The Origin of certain Marbles : a Suggestion ' Sci. Proc. Roy. Dublin Soc. 

 vol. vii (1891; p. 124; see also Haddon, Sollas, & Cole, 'On the Geology of 

 Torres Straits ' Trans. Roy. Irish Acad. vol. xxx (1892-96) pp. 436, 470. 



