Notes on Some Rocks and Minerals — Emerson. 103 
the collection that it is quite sure that they came from Res- 
cue harbor, Field bay, where Hall took ship for his return. 
They are a brownish-black trap-like rock, massive to 
platy, with many deep-red biotite scales showing with the 
lens. 
The rock effervesces for a long time with acid and this 
brings out light-colored spots full of needles of a pyroxenic 
mineral. 
Under the microscope a few large, lemon-yellow serpen- 
tine pseudomor^hs after olivine are surrounded by a broad 
band of the large deep-red biotites which hive an almost 
black border. The change of the olivine is sometimes in 
whole or part into an aggregate of carbonates. Long, 
square prisms of a colorless highly refractive pyroxene oc- 
cur. Another pyroxene appears in tufts of long prisms and 
needles which radiate into calcite-filled cavities. They are 
red-brown in the central half and pale green at the ends. 
Some are wholly dark greenish blue to nearly black. The 
mineral is much like aegerine, but extinguishes at 37 to 41 
■degrees and so is a peculiar pyroxene which has strong ab- 
sorption and dispersion and on being rotated slightly from 
the position of extinction shows red-brown on one side and 
clear blue on the other, suggesting titanaugite. 
Probable remnants of nepheline show uniaxial figure 
and low refraction. Many of these phenocrysts have so 
sharply the trapezohedral cross section as to suggest leucite, 
but these are decomposed in the same way as the prismatic 
forms. 
Half the field is taken up with octagonal or nearly spher- 
ical phenocrysts, which are just visible to the eye. They are 
now mostly decomposed into a mixture of calcite and color- 
less needles. Some show negative uniaxial cross and high 
refraction and polarize in pale blue tints and all are prob- 
ably mellilite. See "Geology of Frobisher's Bay," in Hall's 
Narrative, p. 571, 1879. 
Ahioxtc Porphvry. — Another distinct variety is much 
finer grained than tlie ])receding. It is aplianitic to the eye 
and less distinctly ])orpliyritic to the microscope. 
Tne biotite appears only in the ground with microlites 
of mellilite. The sharj) crystals of amber pyroxene are un- 
