{{Short description|Silicate mineral}} {{Infobox mineral | name = '''Leifite''' | category = Silicate mineral | boxwidth = 24 | boxbgcolor = | image = Leifite-zr4a.jpg | imagesize = 260px | caption = | formula = {{chem2|Na2(Si; Al; Be)7(O; OH; F)14}}<ref name=HOM>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Leifite |url=http://www.handbookofmineralogy.org/pdfs/leifite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=14 March 2022 |date=2005}}</ref> | IMAsymbol = Lf<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = 425.47 g/mol <ref name=Webmin/> | strunz = 9.EH.25 (10 ed) <br /><small>8/J.10-10 (8 ed)</small> | dana = 78.07.10.01 | system = Trigonal | class = Hexagonal scalenohedral ({{overline|3}}m) <br />H-M symbol: ({{overline|3}} 2/m) | symmetry= ''P''{{overline|3}}m1 | colour = white, colourless to pale violet | habit = Typically radiating aggregates of fine needles | twinning = None <ref name=CG>{{Cite web|url=http://www.classicgems.net/gem_leifite.htm|title=ClassicGems.net}}</ref> | cleavage = Distinct on {10{{overline|1}}0} <ref name=Mindat/> | fracture = Uneven to splintery | tenacity = Brittle | mohs = 6 | lustre = Silky to vitreous | refractive = n<sub>ω</sub> = 1.516 and n<sub>ε</sub> = 1.520.<ref name=AM57/> | opticalprop = Uniaxial (+) | birefringence = δ = 0. 011 | pleochroism = | streak = White | gravity = 2.6 | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | other = | references = <ref name=Webmin>{{Cite web|url=http://www.webmineral.com/data/Leifite.shtml|title = Leifite Mineral Data}}</ref><ref name=Mindat>{{Cite web|url=http://www.mindat.org/min-2368.html|title = Leifite}}</ref><ref name=Dana>Gaines et al (1997) Dana’s New Mineralogy Eighth Edition. Wiley </ref><ref name=HOM/><ref name=CM/> }}

'''Leifite''' is a rare tectosilicate. Tectosilicates are built on a framework of tetrahedra with silicon or aluminium at the centre and oxygen at the vertices; they include feldspars and zeolites, but leifite does not belong in either of these categories. It is a member of the leifite group, which includes telyushenkoite {{chem2|(Cs,Na,K)Na6(Be2Al3Si15O39}}) and eirikite {{chem2|KNa6Be2(Si15Al3)O39F2}}).<ref name=Mindat/> Leifite was discovered in 1915, and named after Leif Ericson who was a Norse explorer who lived around 1000 AD, and was probably the first European to land in North America, nearly 500 years before Christopher Columbus.<ref name=Mindat/> Eirikite was named in 2007 after Eirik Raude, or Erik the Red, (950–1003), who discovered Greenland and who was the father of Leif Ericson. The third mineral in the group, telyushenkoite, was discovered in 2001. It was not named after any of Leif Ericson's family members, but after a professor of geology in Turkmenistan.

== Structure == Leifite is a trigonal mineral, class {{overline|3}} 2/m, space group P{{overline|3}}m1.<ref name=CM>Canadian Mineralogist (2002)40:183-192</ref> There are 3 formula units in the unit cell (Z = 3), and cell dimensions are 14.4 Å in the a direction and 4.9 Å in the c direction.<ref name=AM57>American Mineralogist (1972) 57:1006</ref><ref name=BGSD>Bulletin of the Geological Society of Denmark 20:134 (1970)</ref> It contains OH groups, but no water of crystallization as was previously assumed.<ref name=NGT>Norsk Geologisk Tidsskrift (1995) 75:243-246</ref> Tetrahedrons of silicon or aluminium atoms surrounded by four oxygen atoms link to form six-membered rings stacked along the c direction to form channels, similar to those in zeolites.<ref name=CM/>

== Appearance == Leifite is generally white or colourless, with a white streak and a silky or vitreous lustre. It occurs as fine needles making up radiating aggregates and rosettes. Individual crystals are deeply striated hexagonal prisms that are transparent to translucent.<ref name=NGT/>

== Physical Properties == The mineral is hard, with Mohs hardness 6, the same as that of feldspar, and specific gravity 2.6,<ref name=NGT/> again like the feldspars. It is brittle, with an uneven to splintery fracture.<ref name=Mindat/><ref name=HOM/>

== Optical Properties == Leifite is uniaxial(+)<ref name=NGT/> with refractive indices n<sub>ω</sub> = 1.516 and n<sub>ε</sub> = 1.520.<ref name=AM57/> The maximum birefringence δ = 0. 011.<ref name=Mindat/> Leifite is not luminescent.<ref name=CG/>

== Occurrence == The type locality is the Narsaarsuk pegmatite on the Narsaarsuk Plateau, Igaliku, Narsaq, Kujalleq, Greenland<ref name=Mindat/> and type material is kept at the University of Copenhagen, Denmark, and at the National Museum of Natural History in Washington DC, US.<ref name=HOM/> Leifite occurs in cavities in alkali-pegmatite veins.<ref name=Webmin/> At Mont Saint-Hilaire it occurs as crystals up to 5&nbsp;cm long and as disk-shaped aggregates and radially fibrous spheres associated with albite, natrolite, serandite and catapleite.<ref name=Dana/> In Greenland it occurs in a pegmatite with microcline, calcite, zinnwaldite and acmite.<ref name=Dana/> In Russia it occurs in the Lovozero Massif associated with albite and natrolite.<ref name=HOM/> In Norway it occurs in a nepheline syenite pegmatite on the south eastern part of the island of Vesle Aroya in the Langesundsfjord District, Oslo Region, as white to colourless fibrous masses and radiating bundles.<ref name=NGT/>

== References ==

{{Reflist}}

<!--- Categories ---> Category:Silicate minerals Category:Trigonal minerals Category:Minerals in space group 164