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?nd more or less completely filling irregularly-shaped vesicles 

 in the rock. The central greenish (chloride) part is usually 

 almost isotropic, and is surrounded by a zone of yellowish- 

 brown material, with a fibrous structure and a radial arrange- 

 ment of the component parts." 



Professor Hull remarked that olivine was also present in the 

 rock, but according to Professor Cole it is by no means an 

 abundant constituent of the mass. There is no doubt, how- 

 ever, I think, that in some places the rock approaches the 

 nature of an olivine-dolerite, and, that in such portions of the 

 lava, zeolitic minerals are of more common occurrence than 

 purely siliceous ones. To this analysis must also be added 

 iron pyrites, which appears to be distributed in a very irregular 

 fashion throughout the rock. On the whole, it is not a common 

 constituent, but occasional fragments of the rock may be found 

 containing at least five per cent, of the bright, brass-yellow 

 crystals. In the main, we may freely accept Professor Cole's 

 description and nomenclature of the rock as a basaltic-andesite, 

 or allied to the pyroxene-andesites. Although coarser in 

 crystalline structure, the basaltic-andesite of Carnmoney is 

 nearly related to many of the Scottish andesites, which are 

 compact rocks made up chiefly of labradorite, with a smaller 

 proportion of augite, and without olivine ; from these lavas are 

 obtained the finest of the chalcedonies, known as 'Scotch 

 pebbles.' 



2. The Chalcedony of Carnmoney occurs in large cracks, 

 or veins, in the rock. These are sometimes as much as twelve 

 inches in width, and from this, the cavities thin away into a 

 mere hair's-breadth. These veins have apparently been formed 

 during the consolidation of the lava, for the vein-sides are 

 coated, in all degrees of thickness from a mere film to one inch, 

 with the mineral hullitc, which has been described by Professor 

 Cole as "the altered and hydrated glass of the original basaltic 

 ground-mass." As the hot magma hardened, the cooling and 

 crystallisation of the minerals caused mechanical contraction to 

 take place, resulting in the formation of large cracks into which 



