part 2] TERTIARY OUTLIERS OF THE WEST OF ENGLAND. 213 



original matrix) ' probably forms part of the raised beach which 

 fringes Mount's Bay '. 



The minerals identified are enumerated in the table on p. 226. 



On the whole, this is a richer assemblage than that of either 

 the Eocene or the Cretaceous of Devon, and would appear to be 

 in the main locally derived. Kyanite and staurolite are less 

 abundant than in the Pliocene and Cretaceous deposits. Garnets, 

 both colourless and pink, are not uncommon, and, in addition to 

 the minerals obtained from the granite areas (andalusite being 

 very abundant) and the Armorican land-mass, we have horn- 

 blende, serpentine, and epidote. These last-mentioned minerals 

 were probably derived fi-om the rocks of the Lizard, or from 

 that direction. 



Examination of the recent beach-sand from Marazion shows 

 that the mineral assemblage is less rich, and the detrital minerals 

 rather coarser, than in the deposit above described. There are 

 also differences in composition, but these do not appear to be 

 essential. In short, the beach-sand might well have been derived 

 from the Marazion gravel. The petrological evidence bearing on 

 the possible Eocene age of the matrix of the gravel is inconclusive. 



Buckland Brewer, near Bideford. — Loamy deposits and 

 red sands containing Chalk-flints have been described from near 

 Orleigh Court, Buckland Brewer (North Devon). The deposits 

 lie at approximately 260 feet above Ordnance-datum, and are of 

 no great thickness. They rest upon Devonian slates, and can now 

 be observed only in sand-pits in the Rookery and in roadside and 

 hedgerow sections. The flints contained in the loam and sand 

 are weathered to a brown and carious condition. In general 

 characters, the mixture resembles certain of the Eocene and 

 Pliocene deposits farther east, or in places even the ' Clay-with- 

 Flints '. 



After the clay has been washed off and the material sifted, the 

 coarse portion (greater than 1 mm. in diameter) is found to 

 •consist of fragments of grey slate (the local rock), flint-chips, 

 jasper, and grains of transparent, white, and pink quartz, many of 

 the last-named being rounded. The finer material is highly 

 limonitic, and had to be cleared by boiling with dilute hydrochloric 

 acid before separation in heavy liquids. 



The minerals recognized are enumerated in the table on p. 226. 



Tourmaline is by far the most abundant mineral, the grains 

 averaging 0*2 to 0*3 mm. in diameter. Blue crystals as well as 

 brown occur, and one grain was observed, consisting evidently of 

 two united crystals of different orientation, such that it yielded 

 its own interference-tints without an analyser. 



Andalusite is also abundant, and occurs in clear pleochroic 

 grains showing subconchoidal fracture and few inclusions. 



Topaz in large irregular grains is not uncommon. 



Staurolite and kyanite are both rare, only a single grain of 

 the latter having been observed. 



Q. J. G. S, No. 314. q 



