A silver-bearing synthetic variety also exists ( Ag-analcite ).
The alkaline basalt contains olivine and analcite.
Mineral assemblages in phonolite occurrences are usually abundant feldspathoids ( nepheline, sodalite, hauyne, leucite and analcite ) and alkali feldspar ( sanidine, anorthoclase or orthoclase ), and rare sodic plagioclase.
They are found in serpentine and, especially where the lavas contain nepheline or leucite, are often rich in zeolites, such as analcite, prehnite, natrolite, scolecite, chabazite, heulandite, etc.
Paulingite is mostly isotropic and in extreme cases that faint, isolated, fuzzy and weak birefringent twinning which is a determining factor for differentiating paulingite from analcite ( NaAlSi 2 O 6 " H 2 O ).
The missourites are more mafic and consist of leucite, olivine, augite and biotite; the leucite is partly fresh partly altered to analcite, and the rock has a spotted character recalling that of the leucite-syenites.
The name " picrite " can also be applied to an olivine-rich alkali basalt : such picrite consists largely of phenocrysts of olivine and titanium-rich augite pyroxene with minor plagioclase set in a groundmass of augite and more sodic plagioclase and perhaps analcite and biotite.