266 R. H. Rastall — Minerals of Lower Greensand. 



The only minerals occurring in abundance are zircon, kyanite, 

 tourmaline, and staurolite, with small quantities of rutile and 

 epidote and a few crystals of colourless amphibole and pyroxene. 

 The zircons are quite normal and require no special remarks. 

 Tourmaline is abundant and of many coloui*s, including blue, green, 

 olive-green, yellowish-brown, and brown varieties ; the crystals vary 

 a good deal in size and in degree of rounding, some being rather 

 angular, while others are much rolled. Kyanite occurs in large 

 blade-like crystals, often with very sharp edges, as well as in smaller 

 and more rounded grains. Staurolite is unusually abundant in both 

 large and small fragments, the smaller ones being as usual notably 

 sharp and angular. Kutile and epidote are both rare, but of quite 

 ordinary types, the former occurring only in small deep-red prisms. 

 Several crystals of colourless pyroxene were easily identified by 

 1 their high refractive index, strong birefringence, and extinction 

 angles up to 40°. Some rather similar crystals with extinctions up 

 to only 10° appear to be tremolite or some other amphibole. 



As before stated, all samples contained a similar assemblage of 

 heavy minerals, but it was noted that in some cases they were 

 ■distinctly of larger size than in others. This is probably a process of 

 natural sorting, correlated with varying strength of currents, rather 

 than with any actual difference in the sources of the material itself. 

 In such a notoriously current-bedded formation as the Lower 

 Greensand this would naturally be expected to occur, and is 

 evidently not of much significance. 



7. Parish Sand Pit, Aspley Guise. 



This pit, which is situated some 200 yards west of the church, is 

 excavated in the lowest beds of the Greensand, as indicated by an 

 ■examination of the neighbourhood and by the published 1 inch map 

 of the Geological Survey (Sheet 46, Kf.). It shows about 30 feet 

 of yellowish and greyish-white sand, very free from iron, and 

 scarcely at all consolidated ; near the top is a band of fullers' earth 

 about 6 inches thick. 



The process of separation was particularly easy owing to the small 

 amount of iron present. When cleaned in the usual manner a sample 

 of the unseparated sand shows fairly large grains of quartz of 

 remarkably angular forms, together with a good deal of turbid 

 felspar and a little glauconite. The shapes of some of the quartz 

 grains are very curious, as may be seen from Fig. 5. These are, of 

 course, specially selected examples and therefore not truly repre- 

 sentative of the whole, but they are by no means the only peculiar 

 forms present. Rounded and subangular grains of the type usually 

 found in water-borne sands are quite uncommon. 



The heavy minerals that sink in bromoform, though very abundant, 

 are nearly always in quite small grains of very uniform size, 

 averaging about 0'2 ram. in diameter, and very rarely exceeding 

 t)3mm. The non-magnetic portion shows an unusually large 

 number of mineral species. The most important are zircon, 

 tourmaline, staurolite, kyanite, rutile, sphene, pyroxene, and 



