742 ME. J. LOMAS ON THE INOKGANIC [NOV. I9OO, 



Tourmaline. The grains vary much in colour, but green 

 predominates — emerald-green, pistachio-green, blackish- 

 green ; but many are yellow, brown, purple, and a few 

 deep cobalt-blue. The green varieties are mostly angular 

 in form, and often fibrous ; the others are, almost without 

 exception, well rounded. 



The next fraction, with a density slightly less than 3, contains 

 very little but mica and glauconite. 



Both bio tit e and muscovite occur, though muscovite pre- 

 dominates. Associated with the micas is a dark-green 

 biaxial mineral exactly resembling a mica : it is probably 

 sericite. 



Glauconite comes down with this fraction as well as in 

 succeeding separations, even in those lighter than quartz. 

 The heavier forms are opaque, but some of the lighter are 

 translucent and even transparent. By reflected light the 

 opaque varieties are dark-green, with white bands. They 

 often retain the shape of foraminifera, of which they have 

 formed casts. 



The felspars, having a density approximating to that of 

 quartz, are liable to be lost ; but in the examination of 

 many slides I have found microcline, orthoclase, 

 labradorite, and albite. 



Quartz. Even after treatment with strong hydrochloric acid, 

 many of the grains retain a thin staining of iron-oxide. 

 The larger grains only are well-rounded, and some have 

 a very high polish. In size they range from *05 to 

 1'5 millim. Inclusions are very common ; some grains 

 contain so many that they come down with the heavier 

 separations. Apatite is of very frequent occurrence. 

 Most of the grains are colourless, but amethyst- and 

 amber-coloured specimens may be found. In a few cases 

 only was there noticed a trace of secondary crystallization. 

 Small angular pieces of flint and chalcedony are 

 not infrequent. 



The fraction having a specific gravity less than that of quartz 

 consists mainly of glauconite and flint. 



In some localities, as at Walton and places to the south of it, the 

 Red Crag is overlain by sands and gravels. A separate examination 

 of these revealed precisely the same constituents as those enumerated 

 from the Bed Crag. The only distinctions that I could detect were 

 that they contained few or no shell-fragments ; they show very 

 little staining, and the larger pebbles were more numerous. Their 

 general appearance suggests that the Bed Crag material has been 

 sifted by strong currents, the finer stuff and shells being removed, 

 and the larger fragments left. 



