Notes on tJi.e Doleritic Intrusions of East Fife. 449 



Microscopically, the rocks of Crossgates and Radernie have 

 clearly been porphyritic olivine-dolerites, and it is not very difficult 

 to get a picture of the bulk of the original masses as having 

 characters in many respects similar to the rocks of Kilbrackmont 

 and Baldutho. That is to say, they consisted originally of an 

 interwoven mass of elongated plagioclase crystals ; this meshwork 

 enclosing larger and idiomorphic olivines, numerous little idio- 

 morphic prisms of monoclinic pyroxene, ilmenite, uniformly 

 distributed in grotesque skeletal plates, abundant apatite needles, 

 and dark-brown biotite. But the most profound change has 

 dispersed this original mineral assemblage ; the felspars have 

 been dissipated and analcite in large measure taken their place. 

 Every stage in the digestion and replaoemejit of the original plagio- 

 clase can be followed under the microscope. Examined by the 

 method of dark ground illumination, the amount of turbid pinkish 

 analcite can be observed to great advantage. But not only does 

 the analcite permeate all the fabric of the rock, it is also collected 

 into ocelli that are often turbid in the centre and have a pellucid 

 rim that is not uncommonly polygonal in outline. It is interesting 

 to note that the introduction of the analcite has in no way disturbed 

 the original disposition of the unaffected minerals such as the 

 pyroxene. The best method of examining this curious rock is to 

 turn the vibration traces of the nicols slightly aside from 

 rectangularity of intersection so that a dark gray light fills the field 

 of the microscope. The felspar ghosts in respect of the images 

 they afford in the ocular then become easy to discriminate. 



The veins and segregation patches of the Crossgates rock ^ 

 consist of an open meshwork of plagioclase crystals with ophitically 

 related jDurplish pyroxene, and there is an abundant interstitial 

 highly felspathic (alkaline) residue. The felspars range from 

 labradorite to andesine and oligoclase : generally they are much 

 altered and replaced by analcite, (?) albite^ and calcite. The 

 pyroxene is more decidedly purple than in any rock noted so far 

 in this paper ; in this character indicating a j'elationship with the 

 teschenites. Towards its margins the mineral becomes green 

 tinted, or is sometimes bordered by an emerald green substance 

 having different optical properties. As noted, the pyroxene is 

 in part ophitic, but has sharp outlines where it abuts against 

 the residuum. The latter is a turbid brown or reddish-brown 

 aggregate, full of feathery growths of soda-rich felspar, patches 

 of clear or cloudy analcite, shreds of intensely absorbing biotite, 

 granules of iron ore, chlorite, abundant apatite, and a green mineral 

 in flakes and hastate fragments which in respect of its strong 

 birefringence, the negative character of its principal zone, and other 

 optical properties is taken to be aegirine ; also there are occasional 



1 Comparison of this material should be made with some of the rocks described 

 bv Mr. Tyrrell in his valuable paper, " The late Paheozoic Alkaline Igneous 

 Rocks of the West of Scotland," Geol. Mag., 1912, pp. (59 and 120. 



VOL. LIX. — NO. X. 29 



