284 ECONOMIC GEOLOGY. 



lar, pyrites very abundant. Since clay slates occur in considerable 

 quantity in this system, they may be considered typical of the series. 



C consists of crystalline and micaceous limestones not generally 

 traversed by veins of calc spar, in color varying from white to blue, 

 containing numerous caves often partially filled with stalagmitic 

 deposits of crystalline carbonate of lime. 



D is composed of mica, chlorite, and quartzose slates ; ferruginous 

 shales, especially in the upper portion, whilst the lower is often 

 characterized by dark, apparently carbonaceous slates ; the original 

 structure very generally obliterated, but foliation exists in a "high 

 degree. The mica usually distinguished by a green color, contortions 

 frequent, aud quartz veins of still larger dimensions than in section 

 B, attaining a width of from four to six feet. The average dip of 

 this system is from S. 10° W. to S. 10° E. 



The valleys intersecting this district contain alluvial deposits, 

 formed from the degradation of the adjacent hills, and consisting of, 

 1st, large rounded boulders of quartz and tabular pieces of the various 

 rocks just described. 



2d. Beds of smaller boulders and pebbles. 



3d. Soil and vegetable mould ; between them beds of variegated 

 clay often occur, and indeed the boulders, &c., are usually deposited 

 in the matrix of the sa,me nature. 



MINERAL SUBSTANCES ENCOUNTERED IN THE ABOVE FORMATIONS WHICH MAY 

 POSSESS ECONOMIC VALUES. 



The compact limestone of section A forms an excellent material 

 for macadamizing, and is further applicable for the purposes of quick- 

 lime, and for building where roughness of finish is not objectionable, 

 but the production of smooth surfaces, such as characterize firestone, 

 would require too great an expenditure of labor. 



It has been proposed to apply the white limestone (section C) for 

 buildings or inferior marbles ; they would, however, probably be 

 available only for ornamental purposes, as these crystalline limestones 

 require very careful cutting to produce surfaces adapted for construc- 

 tion ; mica contained in these limestones might often communicate a 

 fissile structure, inducing the too facile separation of a block into 

 several pieces. To test their real value it would be judicious to make 

 experiments on the same scale of magnitude as the articles proposed 

 to be manufactured. The portions free from mica are tolerably pure, 

 containing 9G to 97 per cent, of carbonate of lime. (See analysis 

 furnished to the Colonial Secretary.) 



QUARTZ. 



The scattered boulders of this substance, found on the hill-sides or 

 in the beds of rivers, might be employed with advantage for the 

 repair of roads when the limestones are not present. Although very 

 hard, it is not sufficiently tough to resist severe friction. In Saxony 



