IGNEOUS GEOLOGY OF THE BATHGATE AND LINLITHGOW HILLS. 



147 



The Segregation Veins. 



Two varieties of contemporaneous veins occur in the larger sills : — 



(1) " Iron bands," reddish in colour, porous, with miarolitic spaces, and finer or 

 coarser in texture than the surrounding rock ; 



(2) "Blue bands," fine-grained compact and dark-coloured, much resembling basalt, 

 and usually rich in pyrites. 



The composition of both is essentially felspathic, with a small quantity of acicular 

 augite and a varying amount of quartz. A fluidal or trachytic arrangement of the 

 lath-shaped felspars is very apparent in the finer-grained varieties. Augite is more 

 abundant in the blue bands, and is usually much amphibolised and chloritised. The 

 felspar is largely an oligoclase-andesine, much decomposed, although more acid varieties 

 are probably also present. The amount of quartz varies within wide limits, and may 

 sometimes be observed replacing the felspathic material. Pyrites appears to be most 

 abundant in the blue bands. (See PI. III. fig. 4.) The chemical composition is 

 given below. 



The Chemical Composition of the Diabases. 





I. 



II. 



III. 



IV. 



V. 



VI. 



Silica, 



. Si0 2 



48-02 



59-33 



56-22 



51-80 



64-54 



71-26 



Titanium dioxide, 



■ Ti0 2 



3-36 



3-42 



) 





1-22 



0-28 



Alumina, 



. A1 2 3 



13-03 



1286 



V 16-33 



16-43 



13-63 



11-87 



Phosphoric acid, 



• • PA 



0395 



0-388 



J 





0-32 



o-io 



Ferrous oxide, 



. FeO 



9-99 



6-46 



7-94 



10-64 



4-83 



2-12 



Ferrous disulphide, 



. FeS 2 



1-24 



0-215 







1-735 



0-256 



Ferric oxide, . 



. Fe.,0 3 



2-11 



1-88 



3-11 



i-20 



0-22 



o-io 



Manganous oxide, 



. MnO 



trace 



0-14 



0-11 



0-39 



0-20 



0-06 



Lime, 



. CaO 



9-77 



3-74 



5-63 



4-13 



2-31 



2-88 



Magnesia, 



. MgO 



4-21 



2-09 



2-99 



5-76 



1-25 



1-08 



Potash, . 



. K,0 



0-49 



2-15 



1-65 



0-85 



2-28 



054 



Soda, 



. Na 2 



2-17 



5-13 



3-84 



3-81 



5-21 



6-73 



Sulphuric oxide, 



• so 3 



trace 









trace 





Fluorine, 



. F 



0-058 



0-044 







0-056 



0-009 



Combined water, 

 Carbon dioxide, 



: \ 



4-27 



2-12 



1-63 



3-89 



1-86 



2-71 



Moisture, 





1-05 



0-48 



0-88 



1-47 



0-84 



0-62 



100-16 



100-44 



100-33 



100-37 



100-50 



100-12 



I. Dark-coloured modification, somewhat weathered, Kettlestoun Quarry. 

 II. Light-coloured felspathic modification, Kettlestoun Quarry. 



III. Interior of Carribber sill, Carribber Quarry. 



IV. Ocellar margin of Carribber sill, Carribber Glen. 

 V. Blue band, Carribber Quarry. 



VI. Red band, Kettlestoun Quarry. 



The amount of silica in adjoining portions of the sills (I., II.) may apparently vary 

 as much as 10 per cent. The heavy metals vary inversely, and the alkalies directly as 



