PLAGIOCLASE FELDSPARS

Miscellaneous

Notes

(Richard Willis)

Alumino-silicate mineral group comprising the sodium/calcium feldspars. Feldspars are often referred to in terms of two divisions: alkali feldspars, a continuum between orthoclase and albite; and plagioclase feldspars, a continuum between albite and anorthite.
minerals occurrences
albite ———– granites; granitic pegmatites; low-grade metamorphic gneisses and schists
oligoclase —– granodionites and monzonites; arkose; moderate-grade metamorphic rocks
andesine —— diorites; andesites moderate-grade metamorphic rocks, especially amphibolites
labradorite — gabbros and anorthosites; diabases and basalts
bytownite —–– gabbros and anorthosites; diabases and basalts
anorthite —— contact-metamorphosed impure limestone
comparison profile
albite — Ab100
Na2O 11.0, CaO 0.0, Al2O3 19.5, SiO2 68.7, density 2.61, hardness 6-6.5
oligoclase — Ab80An20
Na2O 9.5, CaO 4.0, Al2O3 22.5, SiO2 63.6, density 2.64, hardness 6-6.5
andesine — Ab60An40
Na2O 7.1, CaO 8.1, Al2O3 26.3, SiO2 58.5, density 2.67, hardness 6-6.5
labradorite — Ab40An60
Na2O 4.7, CaO 12.1, Al2O3 29.8, SiO2 53.4, density 2.70, hardness 6-6.5
bytownite — Ab20An80
Na2O 2.4, CaO 16.1, Al2O3 33.2, SiO2 48.3, density 2.73, hardness 6-6.5
anorthite — An100
Na2O 0.0, CaO 20.1, Al2O3 35.6, SiO2 44.3, density 2.76, hardness 6-6.5

Authors

XML

<?xml version="1.0" encoding="UTF-8"?>
<material name="PLAGIOCLASE FELDSPARS" descrip="" generic="0" rawmineral="1" searchkey="" loi="0.00">
<families>
<family name="Feldspar"/>
</families>
<notes>
<note>Alumino-silicate mineral group comprising the sodium/calcium feldspars. Feldspars are often referred to in terms of two divisions: &lt;B&gt;&lt;I&gt;alkali feldspars&lt;/I&gt;&lt;/B&gt;, a continuum between orthoclase and albite; and &lt;B&gt;&lt;I&gt;plagioclase feldspars&lt;/I&gt;&lt;/B&gt;, a continuum between albite and anorthite.&lt;BR&gt;
&lt;B&gt;minerals occurrences&lt;BR&gt;
&lt;/B&gt;&lt;I&gt;albite&lt;/I&gt; &amp;#151;&amp;#151;&amp;#151;&amp;#150; granites; granitic pegmatites; low-grade metamorphic gneisses and schists&lt;BR&gt;
&lt;I&gt;oligoclase&lt;/I&gt; &amp;#151;&amp;#150; granodionites and monzonites; arkose; moderate-grade metamorphic rocks&lt;BR&gt;
&lt;I&gt;andesine&lt;/I&gt; &amp;#151;&amp;#151; diorites; andesites moderate-grade metamorphic rocks, especially amphibolites&lt;BR&gt;
&lt;I&gt;labradorite&lt;/I&gt; &amp;#151; gabbros and anorthosites; diabases and basalts&lt;BR&gt;
&lt;I&gt;bytownite&lt;/I&gt; &amp;#151;&amp;#150;&amp;#150; gabbros and anorthosites; diabases and basalts&lt;BR&gt;
&lt;I&gt;anorthite&lt;/I&gt; &amp;#151;&amp;#151; contact-metamorphosed impure limestone&lt;BR&gt;
&lt;B&gt;comparison profile&lt;/B&gt;&lt;BR&gt;
albite &amp;#151; Ab&lt;FONT SIZE=2&gt;&lt;SUB&gt;100&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O 11.0, CaO 0.0, Al&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;19.5, SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt; 68.7, density 2.61, hardness 6-6.5&lt;BR&gt;
oligoclase &amp;#151; Ab&lt;FONT SIZE=2&gt;&lt;SUB&gt;80&lt;/SUB&gt;&lt;/FONT&gt;An&lt;FONT SIZE=2&gt;&lt;SUB&gt;20&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O 9.5, CaO 4.0, Al&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;22.5, SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;63.6, density 2.64, hardness 6-6.5&lt;BR&gt;
andesine &amp;#151; Ab&lt;FONT SIZE=2&gt;&lt;SUB&gt;60&lt;/SUB&gt;&lt;/FONT&gt;An&lt;FONT SIZE=2&gt;&lt;SUB&gt;40&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O 7.1, CaO 8.1, Al&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;26.3, SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;58.5, density 2.67, hardness 6-6.5&lt;BR&gt;
labradorite &lt;FONT SIZE=2&gt;&amp;#151;&lt;SUB&gt; &lt;/SUB&gt;&lt;/FONT&gt;Ab&lt;FONT SIZE=2&gt;&lt;SUB&gt;40&lt;/SUB&gt;&lt;/FONT&gt;An&lt;FONT SIZE=2&gt;&lt;SUB&gt;60&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O 4.7, CaO 12.1, Al&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;29.8, SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;53.4, density 2.70, hardness 6-6.5&lt;BR&gt;
bytownite &amp;#151; Ab&lt;FONT SIZE=2&gt;&lt;SUB&gt;20&lt;/SUB&gt;&lt;/FONT&gt;An&lt;FONT SIZE=2&gt;&lt;SUB&gt;80&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O 2.4, CaO 16.1, Al&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;33.2, SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;48.3, density 2.73, hardness 6-6.5&lt;BR&gt;
anorthite &amp;#151; An&lt;FONT SIZE=2&gt;&lt;SUB&gt;100&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt;&lt;BR&gt;
&lt;/SUB&gt;Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O 0.0, CaO 20.1, Al&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt; 35.6, SiO&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;&lt;SUB&gt; &lt;/SUB&gt;44.3, density 2.76, hardness 6-6.5&lt;BR&gt;

</note>
</notes>
</material>


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