the spot, and either destroys the remainder by promiscuous cuttings, or
carries them off in bulk, as there are many who go to a locality, and
what they cannot carry off they destroy, give you a disappointment in
finding nothing; consequently, I have considered that this digression
from our subject in detail was pardonable, that one may be independent
of the stated parts of the locality, and not too confidently rely on
them, as I am sometimes disappointed myself in localities and pockets
that I discover in spare time by finding that some one has been there
between times, and carried off the remainder. The characteristics of
magnesite I have detailed under that head under Pavilion Hill, Staten
Island; but it may be well to repeat them briefly here. Form as above
described, from a white to darker dirty color. Specific gravity, 2.8-3;
hardness, about 3.5. Before the blowpipe it is infusible, _and not
reduced to quicklime_, which distinguishes it from dolomite, which it
frequently resembles in the latter's massive form, common here in veins.
It dissolves in acid readily with but little effervescence, which
little, however, distinguishes it from brucite, which it sometimes
resembles and which has a much lower-specific gravity when pure.
_Dolomite_.--This mineral has been very common in this locality.
It differs, perhaps, as I have before explained, from magnesite in
containing lime besides magnesia, and from calc spar by the _vice
versa_. Much of the magnesite in this serpentine contains more or less
lime, and is consequently in places almost pure dolomite, although
crystals are seldom to be found in this outcrop, it all occurring as
veins about a half-inch thick and resembling somewhat the gurhofite
of Staten Island, only that it is softer and less homogeneous in
appearance. Its color is slightly tinged green, and specimens of it are
not peculiarly unique, but perhaps worth removing. Its characteristics
are: first, its burning to quicklime before the blowpipe, distinguishing
it from pure magnesite; second, its slow effervescence in acids. Besides
these, its specific gravity is 2.8, hardness, 8.5; from calcspar it
cannot be distinguished except by chemical analysis, as the two species
blend almost completely with every intermediate stage of composition
into either calc spar, or, what occurs in this locality, aragonite,
similar in composition to it, or dolomite. The color of the last,
however, is generally darker, and it cleaves less readily into its
crystalline form, which is similar to calc spar, and of which it is
harder, 3.5 to 3 of calc spar.
_Aragonite_.--This mineral, identical in composition with calc spar, but
whose crystalline form is entirely different, occurs in this locality in
veins hardly recognizable from the magnesite or dolomite, and running
into dolomite. It is not abundant, and the veins are limited in extent;
the only distinguishment it has from the dolomite, practically, is its
fibrous structure, the fibers being brittle and very coarse. If examined
with a powerful glass, they will be seen to be made up of modified long
prisms. The specific gravity is over 2.9, hardness about 4, unless much
weathered, when it becomes apparently less. There are some small veins
at the north end of the walk, and in them excellent forms may be found
by cutting into the veins.
_Brucite_.--This mineral occurs here in fair abundance, it being one of
the principal localities for it in the United States, and where formerly
extremely unique specimens were to be obtained. It has been pretty well
exhausted, however, and the fine specimens are only to be obtained by
digging into the veins of it in the rock, which are quite abundant on
the south end of the walk, and, as I before noted, as deep as possible
from the top of the veins, as it is a closely packed mineral not