Non-stable rock fragments are composed of K-feldspar with abundant
perthitic lamellae and plagioclase.
Tennis, "A web resource for the study of alkali feldspars and
perthitic textures using light microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy," Journal of Geoscience Education, vol.
The
perthitic potassium feldspar occurs as subhedral to euhedral twinned crystals up to 1.25 cm in diameter.
The feldspar is essentially
perthitic; albite occurs in small quantities.
Lee MR, Parsons I (1995) Microtextural controls on weathering of
perthitic alkali feldspars.
Plagioclase ranges from (23.8% -45.6%) Microcline often intergrown graphically and are sometimes
perthitic with albite occurring as patchy perthite.
On the basis of the relative proportions (volume %) of the three essential minerals, that is,
perthitic alkali feldspar (50-55%), quartz (28-33%), and plagioclase (2-3%), these largely hypidiomorphic and inequigranular to subequigranular rocks fall within the compositional field of alkali feldspar granite (Figure 2).
The main minerals in the sample are quartz,
perthitic orthoclase, plagioclase with sericite, epidote and chlorite.
Pocket zones are characterized by quartz crystals,
perthitic microcline, platy albite, orthoclase, biotite, lithium-iron micas and kaolinite.
The feldspar fraction is dominantly altered orthoclase feldspar and
perthitic ortho-clase feldspar with traces of microcline and plagioclase.
Lee MR, Parsons I (1995) Microtextural controls of weathering of
perthitic alkali feldspars.