Older papers claim that a complete solid solution exists between tetranatrolite and gonnardite, but tetranatrolite was discredited as a separate species in 1999 . A series, based on the disorder of the silicon-aluminum in the framework, appears to exist between Na-rich gonnardite and natrolite, Na 2 ( Si 3 Al 2 ) O 10 ?H 2 O.
22.
Several varieties of natrolite have been distinguished by special names . "'Fargite "'is a red natrolite from Glenfarg in Perthshire . "'Bergmannite "', or "'Spreustein "', is an impure variety which has resulted by the alteration of other minerals, chiefly sodalite, in the augite syenite of southern Norway.
23.
Several varieties of natrolite have been distinguished by special names . "'Fargite "'is a red natrolite from Glenfarg in Perthshire . "'Bergmannite "', or "'Spreustein "', is an impure variety which has resulted by the alteration of other minerals, chiefly sodalite, in the augite syenite of southern Norway.
24.
It also occurs at Yukspor Mountain, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, in an aegerine-natrolite-microcline vein in foyaite, associated with aegirine, anatase, ancylite-( Ce ), barylite, catapleiite, cerite-( Ce ), cerite-( La ), chabazite-( Ca ), edingtonite, fluorapatite, galena, ilmenite, microcline, natrolite, sphalerite and vanadinite.
25.
It also occurs at Yukspor Mountain, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, in an aegerine-natrolite-microcline vein in foyaite, associated with aegirine, anatase, ancylite-( Ce ), barylite, catapleiite, cerite-( Ce ), cerite-( La ), chabazite-( Ca ), edingtonite, fluorapatite, galena, ilmenite, microcline, natrolite, sphalerite and vanadinite.
26.
Generally occurs in Si-poor volcanic rocks, marine basalts and breccias, associated with other sodium zeolites such as analcime, Na ( Si 2 Al ) O 6 �H 2 O, natrolite, Na 2 ( Si 3 Al 2 ) O 10 ?H 2 O, and chabazite-Na, Na 2 Ca ( Si 8 Al 4 ) O 24 ?2H 2 O . It also occurs in Na-rich pegmatites in alkaline rocks, and as an alteration product in some nepheline syenite intrusions.
