NATURAL HISTORY. 
distinct character. Felspar is generally the pre 
dominating ingredient, and frequently occurs in 
large, regular, crystals, of a milk white, or yellow- 
ish white colour, or, more rarely, of a flesh red— 
the quartz is the next, and is not frequently found 
in distinct crystals, tho’ it has the transparency, 
fracture, and other external characters, that denote 
a crystalline texture—the mica, is in thin plates, of 
various size, usually of a smoky brown, or black 
colour—more rarely white, or green—schorl occa- 
sionally forms a componegt part aiso of this forma- 
tion, and chlorite, is found disseminated in small 
earthy grains, or specks, and occasionally enclosed 
in the quartz. —The texture, and other characters 
vary much, from a coarse, to a very fine grain— 
from a compact, and durable character, to an open 
and decomposing one, which latter circumstance is 
probably owing to the presence either of a mineral 
oxide, or an alkali—beds of sand, of various degrees 
of fineness, also occur in different places, and occa- 
sionally decomposed felspar, intermixed with minute 
fragments of quartz, (porcelain clay) as at Horridge, 
in the parish of Ilsington—the general colour of the 
finer, and more compact kinds, is blueish-grey— 
that in a state of decomposition, has usually a 
greater, or less, tinge of yellow, or red, derived 
most probably, from an oxide of Iron, or Manga- 
nese. Remains of old Tin streams, are of very 
frequent occurrence in the granite district. Lodes 
of Tin, micaceous iron, and graphite, or plumbago, 
of inferior quality, occur in this district ; and in the 
