Iron-Bearing Hocks of the Adirondacks. — Nason. 27 
mines, stilbite is found in the crushed mine rock in small but 
perfect crystals. At the same mines small but beautiful crys- 
tals of calcite sparingly occur in "vugs" in the crushed ruck. 
Garnet occurs in the Hope mine at Ring wood, principally in 
the mine rock, and this is the only instance of this kind known 
to the writer. 
Sulphide of iron is constant!}" associated with these ores, 
hut onl} T in three instances abundantly enough to necessitate 
the roasting of the ores before smelting. 
To the country rock of these mines the writer has given 
the name Mt. Hope type.* from a locality where it can he 
easily studied in relation to the bodies of magnetic ore. 
This rock is massively bedded, with only slight traces of 
foliation. It is usually fine-grained, about the same genera] 
texture as the Westerly R. I. granite. 
Its mineral constituents are quartz, orthoclase and plagio- 
clase feldspars, and magnetite. This latter mineral usually 
occurs in rough grains of small size, but it is occasionally ob- 
served in perfect octahedral crystals. The percentage of this 
mineral varies greatly but probably never exceeds 2 to 5%. 
Hornblende and black mica occur. It is noticeable, though, 
that these minerals vary in proportion to the amount of mag- 
netite present. A rock of the above type having a noticeable 
quantity of these minerals, while preserving all of its other 
characteristic-. is almost wanting in magnetite, while if magne- 
tite is present in its usual proportion these minerals are never 
present. 
Zircon is sometimes present in minute crystals. It is 
rarely visible to the naked eye. but thin sections show it to 
exist quite abundantly. 
The color of the rock is very light gray. It strongly resists 
weathering. 
Intimately associated with this rock is a graphite unci--. 
This rock is characterized by the presence of from 1 to L5$ 
of graphite. Magnetite is a very rare mineral. Hornblende 
and black mica are the more prominent non-feldspathic min- 
erals. Contact of this graphite gneiss cither with the above 
rock (Mt. Hope) or with the following described rock has not 
been observed. 
*See Annual Report, State Geologist of N. J., 1889, p. 30. 
