394 A POPULAR TREATISE ON GEMS.
1st.
That sienite which is composed of felspar and hornblende, when the
first is white, greenish, and yellowish, and the latter inyariably
black.
2d.
Felspar, quartz, and hornblende ; the first is foliated, and commonly
of grayish, bluish, or yellowish color; the second from quite light to
dark color and hyaline; and the latter is black. Under this variety the
quarries at Quincy and Cape Ann have been arranged by the author (which
are generally called granite), on account of the absence of mica. The
Quincy granite, or rather sienite, is that celebrated architectural
material used in the cities of Boston and New York, for those huge and
magnificent edifices, public as well as private, erected within the
last six years; and it may be supposed that five thousand buildings in
the city of New York have been constructed with this splendid article.
3d.
Felspar, hornblende, quartz, and mica. This rock, likewise, has a
beautiful appearance, but is, as yet, less wrought than the other
varieties. The felspar and hornblende are predominant. The quartz is
in small grains, and the mica is black.
4th.
Porphyritic sienite; its base is quartz and felspar, and the hornblende
is almost entirely absent; it has a porphyritic aspect; the felspar
predominates. It is the niost ornamental stone when polished.
5th.
Conglomerated sienite; it is a quarternary compound of felspar,
hornblende, quartz, and mica, but all in rounded or conglomerated
masses, having the aspect of a pudding-s'tone; the nodules are from
half an inch to six inches in size, and may be easily broken out of the
mass, and the hornblende predominates mostly in them. It is unfit for
architectural purposes.
6th. Augite sienite; in this rock the hornblende ia present and mica absent. It is composed of black horn-
