Always polysynthetically twinned parallel to [001]
Streak
White
Diaphaneity
Transparent
Specific gravity
2.541
Optical properties
Biaxial (−)
Refractive index
nα = 1.511 nβ = 1.533 nγ = 1.535
Birefringence
δ = 0.023
2V angle
Measured: 29°
References
[2][3][4]
Nyerereite is a very rare sodium calcium carbonate mineral with formula Na2Ca(CO3)2. It forms colorless, platey pseudohexagonal orthorhombic crystals that are typically twinned. It has a specific gravity of 2.54 and indices of refraction of nα=1.511, nβ=1.533 and nγ=1.535. Nyerereite is not stable in contact with the atmosphere and rapidly breaks down. Collection specimens must be kept in a sealed argon environment.
It has a Hermann–Mauguin notation of mm2 and the respective space group is Cmc21.[2] In nature Nyerereite is naturally twinned and is pseudohexagonal with triad twinning; meaning that this is a six sided crystal that apparently has a hexagonal shape but is not in the hexagonal system. Triad twinning is the intergrowth of three orthorhombic crystals that turn at their center and form hexagonally shaped crystals. Nyerereite is biaxial negative, and has a 2v of 29 degrees. It shows a center acute bisectrix and a birefringence of approximately 0.023.[5] At high temperatures or just erupted lava nyerereite is uniaxial and shows an interference color of second order blue when twinning is not present, and when twinning is there the interference color of nyerereite is first order grey.[5]
^http://rruff.geo.arizona.edu/doclib/hom/nyerereite.pdf Handbook of Mineralogy
^ abMckie, D., Frankis, E.J., (1976) Nyerereite: A new volcanic carbonate mineral from Ol Doinyo Lengai, Tanzania. Zeitschrift für Kristallographie 145, 73–95
Nyerereite is a very rare sodium calcium carbonate mineral with formula Na2Ca(CO3)2. It forms colorless, platey pseudohexagonal orthorhombic crystals that...
500–600 °C (932–1,112 °F). The lava is natrocarbonatite dominated by nyerereite and gregoryite. The magmatic origin of carbonatite was argued in detail...
premodern natrocarbonatite volcanism. The main carbonate mineral was nyerereite, which is also the major mineral in present natrocarbonatite lava flows...
Lengai are rich in two rare sodium and potassium carbonate minerals, nyerereite and gregoryite. Due to this unusual composition, the lava is erupted at...
Nontronite Norbergite Normandite Northupite Nosean Nsutite Nuragheite Nyerereite Varieties that are not valid species: Nephrite (variety of tremolite/actinolite)...
Doinyo Lengai volcano of Arusha Region, Tanzania, and the other being nyerereite. Because of its anhydrous nature, gregoryite reacts quickly with the environment...