| Kaersutite | |
| Category: | Inosilicate |
| Formula: | NaCa2(Mg3Ti4+Al)(Si6Al2)O22(O)2 |
| Imasymbol: | Krs[1] |
| Strunz: | 9.DE.10 |
| Dana: | 66.01.03a.18 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | C2/m |
| Color: | Dark brown to black, yellow-brown, green-brown, or red-brown in thin section |
| Habit: | Prismatic phenocrysts, granular aggregates |
| Twinning: | Simple or multiple twinning parallel to |
| Cleavage: | Perfect on, intersecting at 56° and 124° |
| Tenacity: | Brittle |
| Mohs: | 5–6 |
| Luster: | Vitreous |
| Streak: | Pale brownish-grey |
| Diaphaneity: | Semitransparent |
| Gravity: | 3.20 - 3.28 |
| Opticalprop: | Biaxial (−) |
| Refractive: | nα = 1.670 – 1.689 nβ = 1.690 – 1.741 nγ = 1.700 – 1.772 |
| Birefringence: | δ = 0.030 – 0.083 |
| Pleochroism: | Strong; X = yellow, yellow-brown; Y = red, red-brown; Z = deep brown, dark red-brown. |
| 2V: | 66–82° |
| References: | [2] [3] [4] [5] |
Kaersutite is a dark brown to black double chain calcic titanium bearing amphibole mineral with formula: NaCa2(Mg3Ti4+Al)(Si6Al2)O22(O)2.[6]
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]