Galería de Minerales FMF

Para acceder al hilo de FMF donde está la foto

Narsarsukite, Manganoan Pectolite (black)
Kangerdluarsuk, Ilímaussaq Intrusive Complex, Narsaq, Greenland
FoV: 2,5 x 2 cm

GENERAL 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, seen mostly as tabular crystals, parallel to {oo1}.
* NOTE: Neptunite has almost identical formula but different crystal structure; it has monoclinic crystals.
* usually the color is YELLOW
* The type locality is the Narsarsuk pegmatite from where the mineral was described by the Swedish mineralogist Flink in 19O1.

Ilímaussaq Narsarsukite:
* First described from the Ilímaussaq complex by the Russian mineralogist Semenov in 1969
* Occurs in a quartz-bearing contact zone between naujaite and alkaline granite
* This environment is in accordance with:
* "Requisite conditions for narsarsukite growth may be obtained where emanations from alkaline magmas react with siliceous wallrocks" (Stewart (1959), quoted in UPTON et. al. 1977)

* The piece on this photo is from Kangerdluarsuk; where we are near the southern border of the Complex.

Turkestanite:
There are brown prisms (not very much darker than the narsarsukite) in the piece that is turkestanite (pointed out by a trustworthy source who had the piece in his hands). Not very well visible on this view, but there is the squared cross section of a crystal approx in the middle, above the left corner of the long narsarsukite plate. Other day I will try take and load close ups where it is better seen.
* "Ilimaussaq turkestanite forms up to a few millimeter large, brown or brownish-orange, idiomorphic, simple prismatic crystals; associated minerals are microcline, albite, augite, aegirine, quartz eudialyte and narsarsukite." (PETERSEN et.al 1999)

refs:
* STEWART 1959. Narsarsukite from Sage Creek, Sweet Grass Hills, Montana. Amer. Min. 44, 265-73.
(as quoted in: 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)

* PETERSEN et.al: Turkestanite from the Ilímaussaq alkaline complex, South Greenland
Neues Jarhrbuch für Mineralogie - Monatshefte, issue: 9, 1999, pp: 424 - 432
(I did not manage to get the entire article, above sentence is quoted from the abstract) (Author: kakov)