R. H. Rastall — Minerals of Lower Greensand. 215 



The kyanite occurs in prisms, blades, and shapeless grains, the 

 majority being very little rounded, while some are of very peculiar 

 forms, with conspicuous re-entrant angles (Fig. 1). 



Tourmaline shows much variation in size, shape, and colour. It is 

 mostly in good crystals of the usual prismatic forms with flat 

 rhombohedral terminal faces ; the edges are, as a rule, only slightly 

 rounded, if at all. The ordinary well-rounded drop-like forms are 

 much less common. The commonest colour is a brownish green, 

 with resinous lustre ; a few crystals are pure brown. Some more 

 remarkable grains show a brilliant blue colour at the maximum 

 absorption with one nicol prism, while one in particular shows strong 

 pink and blue tints. This is very uncommon. 



Staurolite is as usual in shapeless yellow fragments, nearly always 

 angular in form, a few only showing traces of crystal-faces. Apart 

 from their unusually large average size there is nothing remarkable 

 about them. Rutile, which is not very common, forms red and 

 orange prisms and grains, small and much worn. A few rounded 

 flakes of green mica are a rather unusual constituent. Zircon is 

 rather rare, only a few comparatively large crystals being seen. The 

 other constituents noted in this specimen are, besides ilmenite, brown, 

 yellow, and red opaque grains, presumably consisting of some oxide 

 of iron ; the treatment with acid seems to have been rather incomplete, 

 as compared with specimens of later date, treated by standardized 

 methods. 



Other slides prepared more recently from material from the same 

 pit showed all the minerals mentioned above, with in addition a few 

 crystals of dark-green and bluish hornblende, and colourless and 

 pale-green pyroxene, together with flakes of muscovite. 



One specimen is specially interesting, since it contains a 

 considerable number of rather large grains of garnet, varying from 

 colourless to brownish pink, some being much rounded, while others 

 are very sharply angular and of remarkable forms. These angular 

 chips of garnet are characteristic of many sands of later geological 

 date in the east of England, 1 though it would be hazardous to assume 

 that these were derived from the Sandringham Sands or Carstone. 



One sample from this locality was sufficiently clean and free from 

 iron to be separated and mounted without any preliminary treatment 

 by acid. The chief object of this special examination was to 

 determine the presence or otherwise of minerals soluble in acid, such 

 as might be missed in the ordinary ferruginous samples. This 

 specimen yielded some interesting minerals. Tourmaline was 

 remarkably abundant, most of the grains being brown in colour, but 

 a few were bright blue and one of a clear rose-red. The grains 

 are partly of the usual rounded type, but some are sharply angular, 

 suggesting recent derivation from the parent rock at no great 

 distance. Kyanite and staurolite are common and show nothing 

 unusual ; zircon is rather rare, while rutile occurs frequently both 

 as the usual shapeless bright red grains and as clear prisms with 



1 Eastall, "The Mineral Composition of some Cambridgeshire Sands and 

 Gravels" : Proc. Camb. Phil. Soc, vol. xvii, pp. 136, 138, etc. 



