A linear K release over the period of 1 year was observed for the feldspathoid
nepheline at pH 5, with reduced K release at pH 7.
Frost and Frost (2008) devised a means of classifying alkaline igneous rocks and comparing their geochemistry with "normal" granitic rocks based a plot of alkalinity index (AI) versus feldspathoid
silica saturation index (FSSI) (refer to Fig.
Topaz is a silicate mineral most often found in igneous rocks of felsic (relating to an igneous rock that contains a group of light-colored silicate minerals, including feldspar, feldspathoid
, quartz, and muscovite) composition.
Both the studied rock samples are porphyritic, with a small amount of phenocrysts formed by ferrifassaite passing to sodic ferrifassaite with kaersutite rims, oligoclase-andesine, and minor zeolitized feldspathoid
In its thin sections, the rock has a hypo-crystalline matrix which is composed of porphyritic texture and is rich in a sprinkled opaque mineral, plagioclase, feldspathoid
mineral and obsidian.
It is a partially decomposed granite feldspathoid
having a greater diversity of alkaloids causing it to go into a gradual melt with less surface tension than true feldspars.
24]], a new feldspathoid
mineral from Vesuvius area.
There are 12 types classified in nature along with similar minerals called feldspathoids
such as nepheline syenite.
By other hand, the feldspathoids
presented in the pellets do not have capacity to adsorb EGME.
Likewise, altered feldspathoids
in the nepheline syenites in the Bancroft, Ontario area (formerly called "hydronephelite" or "giesekite") are mixtures of natrolite and muscovite, [+ or -] analcime and other minor constituents.