Another property found in feldspar is complexity or microtexture. For example,
two EDX spectra, (d) and (e), were obtained from the selected areas in Fig. 2.17c.
The EDX spectra of Fig. 2.17d, e corresponds to those of plagioclase and orthoclase
in Fig. 2.13d, respectively.
Using a polished section (Fig. 2.18a), the combination of different minerals and
microtextures in a gravel particle can be observed clearly by using SEM-EDX. The
polished section was prepared by embedding gravel particles in a resin and then
cutting and polishing (see Sect. 1.4). The arrowed particle from Fig. 2.18a was
selected. The optical micrograph (Fig. 2.18b) shows that this gravel particle has
several different parts, weakly transparent, cloudy, and dark. Brown, fine-textured
soil materials partly surround the gravel particle.
The element maps in Fig. 2.18 show that this gravel particle consists of several
different minerals, more than are apparent from the optical micrograph (Fig. 2.18b).
Looking at the Si element map, there are more than three levels of different Si
concentration areas, suggesting different minerals. From these element maps, at least
six different mineral areas can be identified, as listed below (numbered in the Si map
of Fig. 2.18):
(1) An area with high Mg and Fe concentrations and medium Ca concentration.
(2) Areas with the highest Si concentration and near-zero concentrations of other
elements.
Fig. 2.17 Weathered feldspar from the 2–0.2 mm fraction (Fig. 2.16c). (a) Optical micrograph, (b)
SEM image, (c) magnified SEM image of the dashed area in (b), (d and e) EDX spectra of the
dashed areas in (c). The EDX spectra (d) and (e) suggest plagioclase and K-feldspar, respectively
30
2 Primary Minerals
two EDX spectra, (d) and (e), were obtained from the selected areas in Fig. 2.17c.
The EDX spectra of Fig. 2.17d, e corresponds to those of plagioclase and orthoclase
in Fig. 2.13d, respectively.
Using a polished section (Fig. 2.18a), the combination of different minerals and
microtextures in a gravel particle can be observed clearly by using SEM-EDX. The
polished section was prepared by embedding gravel particles in a resin and then
cutting and polishing (see Sect. 1.4). The arrowed particle from Fig. 2.18a was
selected. The optical micrograph (Fig. 2.18b) shows that this gravel particle has
several different parts, weakly transparent, cloudy, and dark. Brown, fine-textured
soil materials partly surround the gravel particle.
The element maps in Fig. 2.18 show that this gravel particle consists of several
different minerals, more than are apparent from the optical micrograph (Fig. 2.18b).
Looking at the Si element map, there are more than three levels of different Si
concentration areas, suggesting different minerals. From these element maps, at least
six different mineral areas can be identified, as listed below (numbered in the Si map
of Fig. 2.18):
(1) An area with high Mg and Fe concentrations and medium Ca concentration.
(2) Areas with the highest Si concentration and near-zero concentrations of other
elements.
Fig. 2.17 Weathered feldspar from the 2–0.2 mm fraction (Fig. 2.16c). (a) Optical micrograph, (b)
SEM image, (c) magnified SEM image of the dashed area in (b), (d and e) EDX spectra of the
dashed areas in (c). The EDX spectra (d) and (e) suggest plagioclase and K-feldspar, respectively
30
2 Primary Minerals