###7 La(W)###Fine###Subangular###Well###Grain###Ferruginous and###Quartz and
alkali feldsparAlso present were small transparent grey grains (with a distinctly higher lustre) of
alkali feldspar that contained tiny metallic hematite flakes and small orange patches, possibly iron hydroxide.
Geological materials such as sand have already been proven excellent adsorbents for theelimination of contaminants from waste water such as Bentonite [9, 10], Chitosan [11], Perlite [12], Kaolin [13], Zeolite [14] and Gypsum [15].The present work evaluates adsorption potential of
alkali feldspar towards Direct Red 16 (synthetic textile dye).
Dominance of plagioclase feldspar over
alkali feldspar is interpreted as being the result of high volcanic input.
In terms of mineral composition, the granite consist of major felsic minerals: quartz (33 %), plagioclase (29 %) and
alkali feldspar (27 %).
The intrusive analogues (theralites, essexitic gabbros, ijolites and essexites) show a holocrystalline inequigranular texture, with diopsidic pyroxene ([Wo.sub.44-51][Fs.sub.8-17]), olivine ([Fo.sub.75-82] to [Fo.sub.44-66]), mica (Ti-phlogopite to Ti-biotite), Timagnetite,
alkali feldspar, and nepheline ([Ne.sub.64-80][Ks.sub.20-36]) [+ or -] leucite [+ or -] amphibole.
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).
It consists mainly of perthitic
alkali feldspar and quartz, and mafic minerals are less abundant than in the quartz alkali-feldspar syenite to alkali-feldspar syenite (Fig.
Chemical weathering of plagioclase,
alkali feldspar, and biotite has formed kaolin which mostly occurs as an anisotropic matrix which pseudomorphs primary minerals (Fig.
A typical rapakivi texture consists of plagioclase-mantled
alkali feldspar megacrysts (ovoids) and two generations of quartz and feldspar.
The latter comprise plagioclase feldspar,
alkali feldspar, quartz, and amphibole that has almost all altered to biotite mica.