CHAP. XXXI 
THE VENTS OF EASTERN FIFE 
79 
The metamorphism of the fragmentary contents of a volcanic funnel by the 
action of ascending vapours has already been described in the case of one of 
the vents of the Carboniferous plateaux (vol. i. p. 404). 
One of the most curious and puzzling features in the contents of the tuff 
necks of the Fife coast is the occurrence there of crystals and fragments of 
minerals, often of considerable size, which do not bear evidence of having- 
been formed in situ, but have undoubtedly been ejected with the other 
detritus. Dr. Hecldle has noticed the fact, and has described some of the 
minerals which occur in this way. The following list comprises the species 
which be and I have found : — 
Hornblende, in rounded fragments of a glassy black cleavable variety. 
Augite, sometimes in small crystals, elsewhere in rounded fragments of an augitic glass. 
Orthoclase (Sanidine), abundant in worn twin crystals in the tuffs of the east of Fife. 
Plagioclase. 
Biotite. 
Pyrope, in the tuffs (and more rarely in the basalts) of Elie. 
Nigrine, common in some of the dykes, more rarely in the tuffs of Elie. 
Saponite, Delessite and other decomposition products. 
Semi-opal, one specimen found in the later (Permian?) agglomerate of Arthur’s Seat. 
Asphalt, abundant at Kincraig, near Elie. 
Fragments of wood, with structure well preserved, may be included here. 
Dr. Heddle has described from the neck of tuff at Kinkell, near St. 
Andrews, large twin crystals of a glassy orthoclase, which are invariably 
much worn, and preserve only rudely the form of crystals. He justly 
remarks that they have no connection with drusy cavity, exfiltration vein, 
or with any other mineral, and look as if a portion of their substance has 
been dissolved away. Internally, however, they are quite fresh and brilliant 
in lustre, though sometimes much fissured. 1 
The tuffs at Elie are full of similar crystals. I obtained from one of 
the necks east of that village a specimen which measures 4 inches in 
length, 3i- in breadth, and 2 j- in thickness, and weighs about 2 lbs. It is, 
however, a well-striated felspar. From the same tuff I procured an ortho- 
clase twin in the Carlsbad form. All the felspar pieces, though fresh and 
brilliant internally, have the same rounded and abraded external appear- 
ance. 
The fragments of hornblende form a characteristic feature in several of 
the Elie dykes (to be afterwards described), and in the neighbourhood of 
these intrusive rocks occur more sparingly in the tuff. It is a glossy -black 
cleavable mineral, in rounded pieces of all sizes, up to that of a small egg. 
Dr. Heddle obtained a cleavage angle of 124° 19', and found on analysis 
that the mineral was hornblende. 2 
Augite occurs sparingly in two forms among the rocks. I have obtained 
small crystals from the red agglomerate on the south side of Arthur Seat, 
recalling in their general appearance those of Somma. Lumps of an augitic 
glass have been found by Dr. Heddle, sometimes as large as a pigeon’s egg, 
in two of the dykes at Elie, and in the tuff at the Kinkell neck, near St. 
1 Trans. Roy. Hoc. Edin. vol. xxviii. p. 223. 2 Op. cit. xxviii. p. 522. 
