No. 275. j 
99 
any thing of the associations of minerals with each other, would at once 
know was perfectly fruitless. The great weight of the hornblende has 
induced others to suppose that iron ore would be found here, which is 
possible, though no workable beds have been as yet discovered. In 
many places there is so much magnetic oxide of iron in the hornblende 
that the magnetic needle will not traverse freely in the vicinity of the 
beds. Where the hornblende is decomposed, a deep red soil is produc- 
ed, coloured by the oxide of iron, and which is highly productive under 
judicious treatment. 
Several quarries may probably be opened to advantage between the 
Hudson, Crom pond and Peekskill. 
VIII. SERPENTINE ROCK. 
This rock is found in several places in New- York, Westchester and 
Putnam counties, but no locality has been observed where it occu- 
pies an area exceeding 100 acres. Dr. Gale has described a locality on 
the island of New- York. A notice of it may be seen in his description 
of the Geology of New- York county, in the appendix to this report.-— 
It is more or less mixed with steatite and a mineral that has been called 
anthophyllite. It is thought that blocks may be obtained suitable for 
ornamental architecture, but it is soft and easily scratched.* 
Another locality of it may be seen on the peninsula east of New- 
Rochelle. It has been quarried to a small extent for a marble, but it is 
understood that good blocks, free from cracks, could not be procured. 
The serpentine at this locality shows almost every shade of colour and 
texture, from black to light yellowish gray, and from compact and crys- 
talline to earthy. It is bounded by hornblendic rocks on the west, and 
by limestone more or less mixed with serpentine and with silicious mat- 
ter on the east. Among the minerals noticed here, may be mentioned 
verd antique^ precious serpentine of a red, green and yellow colour, com- 
mon serpentine, green, yellow, gray, black, compact,, granular and earthy; 
jaspavy chalcedony, agate, drusy quartz, marmolite, hydrate of magnesia, 
carbonate of magnesia, compact and crystalline; tremolite, magnetic ox- 
ide of iron, and chromate of iron ? 
miners soon lost the vein by sinking the shaft vertically, while the seam of plumbago followed 
the layers of the strata parallel to the dip. 
* The term marble is at present restricted to those varieties of limestone that are capable of 
receiving a polish, and which are used for architectural purposes, but I think it would be well 
to include under this term some other substances that are, or may be used for ornamental ar- 
chitecture. Serpentine is one of these, and is called marble by those who have seen it polish- 
ed, and did not know what it was. 
J 
