6 H. C. Sargent—Aainite Veins, Penmaenmauwr. 
Penmaenmawr Mountain. The specimens containing the veins were 
not seen in place, but were collected from the waste-heaps of the 
Graig Lwyd Quarries, the most easterly of the large quarries that are 
making such deadly inroads into the heart of the mountain. Careful 
search on the waste-heaps enabled us to collect further specimens, 
and in some of these the mineral had built in fissures and cracks 
somewhat crowded, very sharp-edged crystals of tabular development. 
I am indebted to the kindness of Dr. G. T. Prior, F.R.S., for the 
identification of the mineral in question as axinite. Several writers 
have made a special study of the Penmaenmawr veins,’ but none of 
them seems to have been aware of the occurrence of axinite in them, 
and a brief description of its habit and associations may therefore be 
not without interest. 
The vein-specimens collected vary in width from 2 inches down- 
wards, but of this thickness the mauve axinite forms only an inner 
subsidiary vein, or veins, varying from half an inch down to 
a sixteenth in thickness. The other portion of the veins is of a light- 
grey colour, and is seen in thin sections to consist of axinite associated 
with a considerable proportion of quartz, the latter mostly in small 
irregular grains and clearly of secondary origin. The quartz some- 
times takes on crystal contours on the edge of the light-grey portion 
of the veins and the crystals then penetrate the subsidiary mauve 
veins. The mauve infilling would therefore appear to be a later 
product than the light-grey axinite. 
The thin sharp-edged crystals developed in fissures and cracks are 
of a pale-brown colour, and their greatest dimension is about a 
quarter of an inch. Sometimes the mineral forms thin radiating 
blades nearly an inch in length. Thin sections of the material in the 
veins do not show crystal outlines, the growth of crystals being 
interfered with by crowding, but cleavage is often well marked—on 
m (110) according to Weinschenk?—and extinctions measured to the 
cleavage-traces have a maximum angle of 42°. Sections which are 
inert, or nearly so, between crossed nicols are, of course, normal, or 
nearly so, to an optic axis. Such sections, in convergent light, show 
only one bar, which bends very slightly on rotation of the stage, thus 
indicating the wide axial angle (2V=72°). The dispersion is very 
marked (p<v). 
Axinite, a borosilicate of lime and alumina, with variable amounts 
of iron, magnesia, manganese, etc., is generally associated with 
calcareous sediments and igneous rocks rich in lime, within the 
contact-aureoles of granites; but that it is of pneumatolytic origin, 
and not a product of thermo-metamorphism, has been shown by 
Messrs. Barrow & Thomas.‘ Its frequent association with prehnite, 
1 See, for instance, Waller, Midland Naturalist, 1885, p. 5; Teall, British 
Petrography, 1888, p. 275; Schaub, Newes Jahrbuch fiir Mimeralome, etc., 
Abh., pp. 108 et seq., 1905; Sargent, Gkou. MAG., Dec. VI, Vol. II, pp. 20-1, 
1915. 
2 Petrographic Methods, trans. Clark, 1912, p. 366. 
3 Weinschenk, op. cit., p. 367. 
4 ** On the occurrence of Metamorphic Minerals in Caleareous Rocks in the 
Bodmin and Camelford areas, Cornwall’’: Mineralogical Magazine, vol. xv, 
pp. 113-23, 1908. 
