Feltspat I. Feltspatmineralenes egenskaper, forekomst og praktiske utnyttelse med særlig henblikk på den norske feltspatindustri.
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The present publication is a description, in non-technical language, of the properties, geological mode of occurrences, exploitation, and uses of feldspar with special reference to the Norwegian feldspar industry. Systematic descriptions of commercial deposits are reserved for a future publication to be issued as no. 128b of the present series. Chapter 1 contains a general description of the mineralogical, chemical, and physical properties of the various species of the feldspar group. - Table I gives the theoretical chemical composition of mixture of potash feldspar and soda feldspar for intervals of 10 pct. by weight. - Table 2 gives the corresponding figures for mixtures of soda feldspar and lime feldspar. - Table 3 contains a few examples of chemical analyses of feldspar from Norwegian occurrences. The analyses, of which No.s 1-5 are new, represent selected, \"pure\" feldspar. No.s 1, 2 and 3 are commercial \"potash feldspars\" from granite pegmatites, No. 4 a soda-potash feldspar from syenite pegmatite, and No. 5 a soda feldspar of commercial quality from a pyroxene bearing granite pegmatite. No.s 6 and 7 are old analyses respectively of oligoclase from granite pegmatite and labradorite from anorthosite. - Table 4 contains multiplication factors for the recalculation of feldspar analyses.