Kaersutite is a dark brown to black double chain calcic titanium bearing amphibole mineral with formula: NaCa2(Mg3Ti4+Al)(Si6Al2)O22(O)2.[6]

Kaersutite
Kaersutite (black) in tuff. Locality: Suletice, Czech Republic
General
CategoryInosilicate
Formula
(repeating unit)
NaCa2(Mg3Ti4+Al)(Si6Al2)O22(O)2
IMA symbolKrs[1]
Strunz classification9.DE.10
Dana classification66.01.03a.18
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Identification
ColorDark brown to black, yellow-brown, green-brown, or red-brown in thin section
Crystal habitPrismatic phenocrysts, granular aggregates
TwinningSimple or multiple twinning parallel to {100}
CleavagePerfect on {110}, intersecting at 56° and 124°
TenacityBrittle
Mohs scale hardness5–6
LusterVitreous
StreakPale brownish-grey
DiaphaneitySemitransparent
Specific gravity3.20 - 3.28
Optical propertiesBiaxial (−)
Refractive indexnα = 1.670 – 1.689 nβ = 1.690 – 1.741 nγ = 1.700 – 1.772
Birefringenceδ = 0.030 – 0.083
PleochroismStrong; X = yellow, yellow-brown; Y = red, red-brown; Z = deep brown, dark red-brown.
2V angle66–82°
References[2][3][4][5]

Ferro-kaersutite is the divalent iron rich endmember of the kaersutite group, with the iron replacing magnesium in the structure.[7]

It occurs as phenocrysts in alkalic volcanic rocks; in nodules of peridotite and gabbro in alkalic basalts; in syenites, monzonites and carbonatite tuffs. Mineral association includes titanian augite, rhoenite, olivine, ilmenite, spinel, plagioclase and titanian pargasite.[2]

It was first described in 1884 and is named for Qaersut (formerly Kaersut), Umanq district in northern Greenland.[3]

References

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  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b "Kaersutite" (PDF). Handbook of Mineralogy. Retrieved 2024-03-21.
  3. ^ a b http://www.mindat.org/min-2129.html Mindat: Kaersutite
  4. ^ http://www.webmineral.com/data/Kaersutite.shtml Webmineral data
  5. ^ "IMA Master List". Archived from the original on 2015-01-05. Retrieved 2014-05-12.
  6. ^ http://www.minsocam.org/msa/ammin/toc/Abstracts/2012_Abstracts/ND12_Abstracts/Hawthorne_p2031_12.pdf [bare URL PDF]
  7. ^ Ferro-kaersutite on Mindat