Calcite by effervescing on placing a drop of acid upon it. Natrolite resembles stilbite, but may be distinguished by gelatinizing readily with hydrochloric acid and by not intumescing when heated before the blowpipe; from the other minerals by the form of the crystals and their setting, also the locality in the tunnel in which it was found.

Pectolite sometimes resembles some of the others, but may be readily distinguished by its tough long fibers, not brittle like natrolite. Datholite may generally be distinguished by the form of its crystals and their glassy appearance, with great hardness, and by tingeing the flame from the blowpipe of a true green color. Apopholite is distinguished from calcite, as noticed under that species, and from the others by its form, difficult fusibility, and part solubility.

Phrenite is characterized by its hardness, greenish color, occurrence, and action of acid. Iron pyrites is always known by its brassy metallic aspect and great hardness. Copper pyrites, by its aspect from the other minerals, and from iron pyrites by its inferior hardness and less gravity.

Stilbite is characterized by its form, difficult gelatinizing, and intumescence before the blowpipe; from natrolite as mentioned under that species.

Laumonite is known by its generally chalky appearance and a probable failure in finding it.

Heulandite is distinguished from stilbite by its crystals and perfect solubility; from apopholite by form of crystals.

In the next part of this paper I will commence with Staten Island.

July 1, 1882. (To be continued.)