No. 161.] 
59 
stalactitical and mammillary form, slightly fibrous; specific gravity, 
the mean of two trials, with as pure a specimen as I could obtain, 
2.305. It contains 33 per cent of water. In addition to the alu- 
mina, I also found silica and oxide of iron, but could not determine 
whether these were accidental or formed part of the mineral.* 
Mica, — Specimens of this mineral, of great beauty, were ob- 
tained near Pope's mill, St. Lawrence county. They are in the 
form of six-sided tables, some of them upwards of six inches in 
diameter. 
Garnet. — The beautiful variety, called Colophonite, occurs in 
great abundance, associated with Tabular Spar, in the town of 
Lewis, Essex county, nine miles south of Keeseville. 
Feldspar. — The iridescent variety, resembling that from La- 
brador, of which I obtained a specimen from Dr. Thomas, of Keese- 
ville, is said to be found in abundance on the head waters of the 
Hudson. The same mineral is also found, of uncommon beauty, 
in boulders, near Ogdensburgh, St. Lawrence county, as first point- 
ed out by Dr. J. B. Crawe. 
^Lignite — On Staten Island, near Rossville, is a stratum of this 
mineral, from three to six inches in width, apparently below high 
water mark. Sometimes it has the colour and appearance of 
wood; at others, it is quite compact, and has a dark brown or 
black colour, and resembles jet. Crystals of iron pyrites occur 
in the fissures of the lignite, and these are often of great beauty; 
but after being exposed to the air they are usually converted into 
sulphate of iron. Probably, also, amber will be found here, as it 
accompanies a similar formation at South Amboy, in New-Jersey, 
a few miles from the above locality. 
Pyrolusite — Binoxide of Manganese. — Small masses, which I 
believe are to be referred to this species, were found in the mar- 
ble quarries at Sing-Sing; where I also observed efflorescences of 
blue carbonate of copper. 
Sulphuret of Molybdenum. — Specimens of this mineral, from 
Clinton county, were receive through Mr. J. Hochstrasser. 
* Dr. Thomson suggests that it is a congeries of hydrates. Outlines of Mineralogy, 
Geology, &c. I. 222. 
