Sixth, granular marble , which consists entirely 
of crystals of carbonate of linte ; and which, 
when its colour is white, and texture fine, is the 
substance used by statuaries. 
Seventh, chlorite schist , which consists of chlo- 
rite, a green or grey substance, somewhat analo- 
gous to mica and feldspar. 
Eighth, quartzose rock, which is composed of 
quartz in a granular form, sometimes united to 
small quantities of the crystalline elements, which 
have been mentioned as belonging to the other 
rocks. 
The secondary rocks are more numerous than 
the primary ; but twelve varieties include all that 
are usually found in these islands. 
First, grauwacke , which consists of fragments 
of quartz, or chlorite schist, embedded in a 
cement, principally composed of feldspar. 
Second, siliceous sandstone , which is composed of 
fine quartz or sand, united by a siliceous cement. 
Third, limestone , consisting of carbonate of lime, 
more compact in its texture than in the granular 
marble ; and often abounding in marine exuvia. 
Fourth, aluminous schist or shale , consisting of 
the decomposed materials of different rocks ce- 
mented by a small quantity of ferruginous or 
siliceous matter ; and often containing the impres- 
sions of vegetables. 
Fifth calcareous sandstone , which is calcareous 
sand, cemented by calcareous matter. 
Sixth, ironstone , formed of nearly the same 
materials as aluminous schist, or shale ; but con- 
taining a much larger quantity of oxide of iron. 
