Alkali feldspars from pegmatite of Brazil and Spain have microscopic to submicroscopic inclusions giving a >turbid> and >clouded> appearance. Inclusions are isotropic, irregular and spatially associated with patch/vein lamellae in network and/Or isolated masses. Inclusions have no detectable lines in XRD and microprobe analyses show strong variability: Si02 40-46 wt%, Al203 30-40 wt%, Kp up to 5 wt%, Nap up to 0.5 wt%, FeO up to 2.5 wt%, MgO up to 1.3 wt%, CaO up to 0.4 wt%, pps up to 0.35 wt%, F up to 2000 ppm, Cl up to 5500 ppm. Dark coronas around them are richer in Cl, Fe, Mg. Thermal analysis up to 600°C shows a TG curve with multiple steps of water loss up to 11 wt%. A homogeneous matrix with a clot appearance is observed in transmission electron microscopy containing crystals inside. Electron diffraction patterns show an amorphous nature. 29Si-MAS¿NMR spectra show one or two broad lines at approximately -87 and -91.6 ppm from Si in the Q3 environment. TI Al-MAS-NMR spectra show one or two broad lines at approximately -70 and -3 ppm due to Al in IV and VI coordination. Inclusions with a >turbid> appearance are kaolin-like amorphous materials. They may be interpreted as a product of the interaction of early rock with Cl-rich aqueous fluids from the late transformation stage in the pegmatite process. This interaction is associated with Na-feldspar patch/vein-lamellae formation of perthites.

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