- The
feldspathoids are a
group of
tectosilicate minerals which resemble feldspars but have a
different structure and much
lower silica content. They occur...
-
gabbro contains up to 10%
feldspathoids rather than quartz. "Foid" in the name is
usually replaced by the
specific feldspathoid that is most
abundant in...
- at
least 10% of the
mineral content consists of quartz, feldspar, or
feldspathoid minerals,
classification begins with the QAPF diagram. The
relative abundances...
-
Ancient Gr**** νεφέλη (nephélē) 'cloud'), is a rock-forming
mineral in the
feldspathoid group – a silica-undersaturated aluminosilicate, Na3KAl4Si4O16, that...
-
essential alkali feldspar.
Relatively minor plagioclase and
quartz or a
feldspathoid such as
nepheline may also be present. This is
reflected in the position...
-
approximately equal amounts.
Quartz is less than five
percent and is
absent in a
feldspathoid-bearing latite, and
olivine is
absent in a quartz-bearing latite. When...
-
olivine Es****ite –
Igneous rock type Foidolite –
Igneous rock rich in
feldspathoid minerals Gabbro – Co****-grained
mafic intrusive rock Granite – Type...
- The
acronym QAPF
stands for "Quartz,
Alkali feldspar, Plagioclase,
Feldspathoid (Foid)",
which are the four
mineral groups used for
classification in...
-
substitution by Al3+. As a result,
feldspathoids are
almost never found in ****ociation with quartz. A
common example of a
feldspathoid is
nepheline ((Na, K)AlSiO4);...
- some are
peralkaline (terms
discussed in
igneous rock).
Nepheline is a
feldspathoid, a solid-solution mineral, that does not
coexist with quartz; rather...
