218 
PETROLOGY OF LOCAL PEBBLES. 
Sep., 1889 
There are, in addition, a number of small blades or needles 
of tourmaline of more usual appearance. The specimen has 
been much cracked, faulted, and recemented. The cracks 
have been filled up with quartz, which is traversed by needles 
of tourmaline, showing up very beautifully in the transparent 
quartz. 
(11) Tourmaline schist (5) from King’s Heath. 
Beautifully crystallised schist, with a fine set of micro¬ 
faults. The quartz of the veins is larger grained than that 
of the body of the rock, and contains, as in the last case, 
needles of tourmaline radiating from the walls of the crack. 
(12) Breccia from Alvechurcli (8). 
Exactly similar pebbles occur at King’s Heath and Sutton. 
It has the appearance of quartz rock which contained a 
few fine strings of tourmaline — it scarcelv amounts to a 
tourmaline schist — broken up and cemented by a mass 
containing a much larger proportion of tourmaline, in many 
parts containing very little else. In hand specimens and 
in sections to the naked eye, the brecciated character is 
obvious, but from the fact of the original tourmaline and 
that of the cement being of just the same appearance, the 
whole has, under the microscope, the aspect of a quartz 
tourmaline rock in which the latter mineral has aggregated 
into clots and strings. 
(18) Appears like a quartz felsite which has been sub¬ 
jected to strong alteration. The specimen (from King’s 
Heath, No. 12) has a sparkling, obviously crystalline ground, 
in which large quartz grains are visible to the naked eye. 
There are numerous aggregated masses of crystals of black 
tourmaline, which in many cases have rectangular outline? 
indicating the replacement of felspar. 
Under the microscope the tourmaline presents the usual 
characters, but is more widely disseminated through the 
section than appears macroscopically. The ground shows a 
mosaic polarisation in quite considerable sized grains, and 
there are no certain indications of any mineral but quartz 
composing it. 
The larger porphyritic quartz grains are rounded, not 
very numerous in the section examined, and contain fine 
acicular crystals of a pale yellowish green, which do not show 
any definite faces from which to form a judgment as to 
their nature. There are also numerous fluid cavities, and in 
one or two of the grains the little crystals are arranged 
almost concentrically, the section being very nearly at right 
angles to the principal axis of the quartz. The quartz of the 
