Notes on the Doleritlc loitriisions of East Fife. 451 



analcite, there is little doubt that the greater part of this mineral 

 is entirely secondary. The teschenites of the Edinburgh district, 

 of East Lothian, and of the Glasgow district, all bear abundant 

 testimony to the accuracy of that opinion. Large tracts of usually 

 turbid analcite in these rocks are simply the replacement products 

 of plagioclase felspar, though perhaps only a parallel orientation 

 of decomposition products along what formerly were cleavage 

 cracks may remain to mark the one-time presence of that mineral. 

 The teschenites are in some respects noteworthy for the capricious 

 disposition of their constituents, for the same mass will often show 

 highly analcitic areas or, again, parts that are richer in hornblende, 

 pyroxene, or biotite, and this without any large scale differentiation 

 of the mass in situ. 



The Spalefield teschenite is interesting on account of its beautifully 

 fresh olivine. In the southern portion of the quarry in which the 

 rock is exposed, a more highly felspathic variety can be collected. 

 Occasionally large areas of turbid analcite enclose partially re])laced 

 felspar, that is albite-oligoclase : it is probably this mineral that 

 Dr. Flett commented upon as having a deceptive resemblance 

 to nepheline. 



The rock of Kingask may be referred to here, though it is neither 

 a typical teschenite nor a typical picrite. But it has affinities with 

 both. The quarry where the mass is exposed is situated about 

 3 miles to the east of St. Andrew's on the north side of the main 

 road that nms to Crail. The. rock weathers spheroidal! y, and is in 

 places highly decomposed. On the south-east side of the exposure 

 the igneous mass is seen to make junction with sandy sediments 

 that have been highly altered and in places partly recrystallized. 

 The intrusion appears to have been initially at a high temperature, 

 and in one place a number of small spheroids of sediment were noted 

 in the igneous rock apparently in process of digestion. The rock 

 is extremel}^ hard and has a first-class reputation as a road-stone, 

 being durable and an excellent " binder ". 



Microscopically, the rock can be seen to have a high content 

 of olivine, sometimes completely in the condition of serpentine, 

 frequently remarkably fresh and unchanged. Analcite is abundant 

 in pellucid patches, but often turbid and replacing plagioclase 

 felspar ; the latter showing the usual range present in the olivine- 

 dolerites. Purplish and brownish pyroxene is an essential ingredient 

 of the rock, the crystals having a good development of the front and 

 back pmakoids, being elongated parallel to the crystal axis c and 

 generally idiomorphic except where abutting against olivine. The 

 subordinate constituents include apatite, magnetite, biotite, and 

 zeolites. Where the rock makes contact with the sediments, a more 

 teschenitic facies is taken on, much richer in biotite and resembling 

 m striking fashion some portions of the rock of Spalefield. 



These fragmentary notes may be concluded with an expression 

 of the hope that some systematic investigation may at no distant 



