GE:or^OGY OF IvA SAIvIvE: COUNTY. 



69 



ones on either bank for a mile or more in either direc 

 tion. About La Salle the same phenomena are seen, 

 especially between La Salle and the tunnel, along* the 

 C.,R.I.& P.R.R. Such is an outline of the geolog-y of 

 La Salle county, and a brief summary of its resources. 

 These are great, and if they are carefully developed 

 in an intellig'ent and thorougfh manner it cannot fail to 

 become one of the richest and most populous counties 

 in the State. Too little attention has been paid to these 

 matters hitherto, and the efforts made to induce capi- 

 tal to invest in this work of development have been far 

 from enlig-htened and very spasmodic. La Salle county 

 could well afford to pay for a complete g-eolog*ical sur- 

 vey and to publish a report in good style. It would 

 cost perhaps $500 per jea-v for a couple of years, but it 

 would repay this a hundred fold. 



MINERALOGY. 



The minerals of La Salle county are not numerous 

 nor of great beauty, but they are of much greater 

 economical value than those which would be more 

 likely to dazzle the eye or fire the imagination. They 

 are mostly compounds of lime, alumina, iron and coal. 



Galenite, Galena; 44, sulphate of lead; sulphur, 

 13.4; lead, 86.6; lusture metallic; color, and where 

 scratched lead gray; easily scratched; heavy crystal- 

 ized usually in cubes. Found in Trenton limestone in 

 small quantities. 



Pyrite, 75, bisulphide of iron, sulphur, 53.3; iron, 

 46.7; pale brass yellow, when scratched greenish 

 black, hard with metallic lusture, in cubes and various 

 forms. Abundant in coal and the clays, both above 

 and below the coal. 



Marcasite, 90; composition same as pyrite; pale 

 bronze yellow, inclined to green or gray; hard, brittle' 

 radiated, like a coxcomb, etc.; associated with pyrite; 

 is more liable to decompose than pyrite. 



