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Narsarsukite
Island of Igdlutalik, Narsaq, South Greenland
FoV: 2,5 x 2 cm

GENERAL info about the mineral:
* Narsarsukite is a titanium containing chain silicate known currently from around 20 alkaline localities worldwide.
* General formula is Na2(Ti,Fe)Si4O11 - may contain F and OH
* Tetragonal crystal forms, mostly plates
* NOTE: Neptunite has almost identical formula but different crystal structure; it has monoclinic crystals.
* The type locality is Narsarsuk (xxx complex) from where the mineral was described by the Swedish mineralogist Flink in 19O1.

My previous photo of Narsarsukite from Ilímaussaq show a more typical aspect of the mineral, i.e. yellow plates.
The following is information about the PARTICULAR Igdlutalik Narsarsukite on this photo (source in the end):

The SITE :
* Igdlutalik is NOT inside, rather 12 km west of the Ilimaussaq complex. (and 45 km west of the type locality Narsarsuk)
* Narsarsukite occurs at the island within a dyke of peralkaline trachyte.
* The dyke was found during the 1 : 2o ooo reconnaissance mapping of the Julianehaab area by the Greenland Geological Survey.
* It is some 20 m wide and the outcrop can be traced not more than 50 m along the length of the dyke.

The CRYSTALS of Igdlutalik Narsarsukite:
* Short prisms (around twice as long as they are broad) unlike most narsarsukite from other locations that have tabular habits.
* Forms {1oo} and {oo1} are dominant
* The unique GREEN color here is probably due to aegirine inclusions. (the mineral itself is normally yellow)

COMPOSITION - particularities:
* The Igdlutalik narsarsukite has a distinctly high Ti/Fe ratio compared with those from Ilimaussaq and Narssarssuk; in this respect it most closely resembles the Sweet Grass, Montana narsarsukites (Stewart, 1959).
* Niobium is a significant minor component

FORMATION:
* All known occurrences of narsarsukite are in silica-oversaturated environments in close association with alkaline intrusive rocks that have crystallized at relative low pressures.
* Stewart (1959) pointed out that the requisite conditions for narsarsukite growth may be obtained where emanations from alkaline magmas react with siliceous wallrocks.
* Growth of narsarsukite, according to Stewart (I959), requires an excess of silica, high partial pressure of oxygen, and all abundance of Ti and Na. Stewart considered that at lower oxygen pressure neptunite, Na2FeTiSi4O12, would be generated. However, Rajasekaran (I966) demonstrated the apparently stable coexistence of narsarsukite and neptunite at St. Hilalre, Quebec.

SOURCE OF INFORMATION - most of the above is directly extracted from:
UPTON et. al. : Narsarsukite - a new occurrence in peralkaline trachyte, south Greenland
Mineralogical Magazine, Sept 1976, Vol. 40 PP. 737-46
www.minersoc.org/pages/Archive-MM/Volume_40/40-315-737.pdf‎
(giving all the references I have left in the above extracts)

on Mindat:
* Igdlutalik, the locality : http://www.mindat.org/loc-23311.html (by the way it is the type locality for Emeleusite)
* Narsarsukite crystals from the same dyke http://www.mindat.org/locentry-156911.html (Author: kakov)