NORTHSIDE SITE
Plane polarized light is just
visible light under the microscope. Crossed (X) polarized light
allows you to see mineral characteristics such as twinning in the
feldspar and alteration. At 2.5X magnification, the distance
across the slide is 4.8 mm and at 10 X magnification it is about
1.2 mm.
NS-56: This sherd is much coarser than
NS-21. It also has a lot of coarse (rounded to blocky to
subangular; quartz + feldspar mineral grains; 1.6 x 1.4 mm down
to 1.0 x 0.4 mm) shale fragments as temper. In addition, there
are also rock fragments (plagioclase + quartz) and some
polycrystalline rounded (to subrounded) aggregates of feldspar
(possibly devitrified ash as they have sutured grain boundaries,
~1.5 x 1.0 mm). The remainder of the temper material is feldspar
(some are Carlsbad twinned, thus might be K-spar) and quartz
(mostly monocrystalline, ~1.2 x 0.8 mm).
(2.5 X plane polarized light) Angular
plagioclase + k-spar rock fragments.
(2.5 X plane polarized light) Subrounded shale
fragment (lower left) and rock fragment (centre, subrounded to
subangular) composed of amphibole + feldspar + quartz.
(2.5 X plane polarized light) Blocky to
rounded shale fragments (Note the separation void around them.
This is a result of differences in behaviour during cooling after
firing).
NS-21: This sherd is medium to fine
grained, with a brown-red paste color. There are recognizable
oxidation rims on either side of the sherd (0.4 to 0.8 mm on one
side and ~0.2 mm on the other side. There are a few large,
rounded, shale fragments ( ~1.8 x 1.2 mm) that have quartz +
feldspar grains. The remainder of the temper is a mixture of
quartz (both monocrystalline and polycrystalline) and plagioclase
mineral grains. There are a few altered (devitrified?) ash
/pumice fragments and a few remnants (actually void spaces) that
appear to once have been shell fragments. Whether they were
weathered out or that the firing temperature was at a temperature
that they were consumed cannot be determined.
(2.5 X plane polarized light) Much
finer-grained than NS-56. Note shell fragment void (right of
centre - long mollusk fragment), shale fragments (upper left of
centre), and a blocky rock fragment (left of centre below shale
fragment) and the size of remainder of temper (around 0.1 mm size
– similar to that of the paste).
(2.5 X plane polarized light) Angular
plagioclase + k-spar rock fragments. 
(2.5 X plane polarized light) Subrounded shale
fragment (lower left) and rock fragment (centre, subrounded to
subangular) composed of amphibole + feldspar + quartz. 
(2.5 X plane polarized light) Blocky to
rounded shale fragments (Note the separation void around them.
This is a result of differences in behaviour during cooling after
firing). 
(2.5 X plane polarized light) Much
finer-grained than NS-56. Note shell fragment void (right of
centre - long mollusk fragment), shale fragments (upper left of
centre), and a blocky rock fragment (left of centre below shale
fragment) and the size of remainder of temper (around 0.1 mm size
– similar to that of the paste).