LAE SPE LPROGKRAPILACAL PROVINCE OF ESSEX. COUNTY 791 
eral olive-green and highly pleochroic; ¢—dark olive-green, 
b= dark greenish-brown, a —yellowish-green. The absorption 
isu Di de bhexextinction angle eva ise hich: about.20° 
having been observed in sections cut nearly parallel to (010). 
In certain specimens, notably those from Eastern Point 
(Gloucester) and Magnolia, a bluish hornblende occurs not 
only as separate crystals, but as patches in the green horn- 
blende, and is also found forming a fringe on the ends of large 
crystals of this mineral. This occurrence is somewhat analogous 
to that described by Cross* in a dike in Colorado, where he 
regards the blue hornblende as secondary. His dike was much 
decomposed, while these granites are quite fresh; but it seems 
probable that here also part of the blue hornblende is secondary. 
As will be seen later, they are quite common in the region, and 
in many cases are undoubtedly primary. Inclusions in horn- 
blende are not abundant, a few grains of magnetite, allanite, 
zircon, and apatite having been seen. The green hornblende 
often yields a secondary brown biotite on decomposition. 
Biotite is a very common constituent, the greater part being 
primary. The granite near Manchester, represented by speci- 
mens from several quarries, is essentially a biotite-granite, horn- 
blende being absent. In the majority of occurrences, however, 
the biotite accompanies hornblende, and is present in less 
amount. Two varieties are found. One is very pale green, 
with rather weak pleochroism, the colors being almost colorless 
and delicate apple-green. This is probably to be referred to the 
cryophyllite discovered by Cooke,’ and investigated by Clarke 
and Riggs. The other, which is more abundant, is darker 
greenish-gray, and shows stronger pleochroism; a deep, almost 
opaque, greenish-gray and a pale olive-green. Sections parallel 
to the base show in convergent light a marked opening of the 
optic axes. This biotite is referred to lepidomelane (annite), 
but Clarke’s researches have shown that several varieties exist. 
«Cross, Am. J. Sci., Vol. XXIX, p. 359, 1890. 
2]. P. CooxE, Am. J. Sci. (2), Vol. XLIII, p. 217, 1867. 
3F, W. CLARKE, Am. J. Sci. (3), Vol. XXXII, p. 358, 1886. 
