Epistolite

epistolite

murmanite

pectolite

steenstrupine

Images

Formula: (Na☐)Nb2Na3Ti(Si2O7)2O2(OH)2(H2O)4
Sorosilicate (Si2O7 groups), lamprophyllite group
Specific gravity: 2.65 to 2.89
Hardness: 2½ to 3
Streak: White
Colour: White, yellowish grey, pinkish beige, tan, silver on {001}
Common impurities: Al,Ta,Fe,Mn,Mg,Ca,K,F,P
Environments

Plutonic igneous environments
Pegmatites
Hydrothermal environments

Epistolite is a low temperature mineral in alkalic pegmatites, albitites, sodalite xenoliths and hydrothermal veins. It is a rare mineral of nepheline syenite massifs. Associated minerals include aegirine, albite, murmanite, sphalerite, manganoan pectolite, neptunite, steenstrupine, rinkite, sodalite, eudialyte and nenadkevichite (HOM, Dana).
Epistolite alters to nenadkevichite, gerasimovskite and other minerals (Dana). It forms syntactic intergrowths with murmanite (CM 43: 973-987).

Localities

At the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, some epistolite may be an alteration product of vuonnemite (Dana).

At the type locality, Nunarssuatsiaq, Tunulliarfik Fjord, Ilímaussaq complex, Kujalleq, Greenland, epistolite occurs in a nepheline syenite pegmatite (Dana).

In the Lovozersky District, Murmansk Oblast, Russia, epistolite occurs in ussingite pegmatites (Dana).

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