Description: 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)

All pictures, text, design © Forum FMF 2006-2024