T. 8. Hunt on the Crystalline Limestones of N. America. 195 
plumbago, and their hardness to intermingled grains of rounded 
silicious sand. The limestone is often magnesian, and the man- 
tr in which the beds of dolomite are iuterstratified with the 
pure limestone, is such as to lead us to suppose that some of the 
original sedimentary deposits contained the two carbonates, and 
that the dolomite is not the result of any subsequent process. 
The principal mineral species found in these limestones are 
apatite, serpentine, phlogopite, scapolite, orthoclase, pyroxene, 
wollastonite, idocrase, garnet, brown tourmaline, chondrodite, spi- 
nel, corundum, zircon, sphene and graphite. All of these appear 
to belong to the stratification, and the chondrodite and graphite 
especially, are seen running in bands parallel to the bedding. 
Magnetic iron ore is sometimes found in beds interstratified with 
the limestone. The apatite which is in general sparingly dis- 
tributed, is occasionally very abundant in imperfect crystals and 
irregular crystalline masses, giving to small beds of the limestone 
the aspect of a conglomerate. Some of the coarsely crystalline 
Farther south, they become the white granular marbles of western 
Vermont, and of Berkshire, Massachusetts, which according to 
Hall, still exhibit upon their weathered surfaces, the fossils of the 
i t, they cross the 
near West Point, and appear in Orange and Rockland 
counties, New York, and in Sussex county, New Jersey, in a 
highly altered condition, closely resembling the erystalliue lime- 
hes of the Laurentian series, and containing in great abund- 
ace the same imbedded minerals. ‘These limestones are some- 
