Nyerereite

From Wikipedia, the free encyclopedia

Nyerereite has a chemical composition of Na2Ca(CO3)2 where the alkali element is clearly present, and has an important role when the magma reaches the surface. Nyrereite is orthorhombicpyramidal and has a Hermann-Mauguin symbol of mm2 and the respective space group is Cmc21.[1] In nature Nyerereite is naturally twinned, as described before by Grittin (1998) nyrereite is pseudohexagonal and has 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. [2] 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. The appearance this mineral is tubular with {001} faces well developed and no proper faces down the [001] zone.[2]

[edit] Special Characteristics

Since nyerereite is very unstable when it reaches the surface if creates pseudomorphs,[3] which is basically the process by the appearance and dimensions remain constant but the main mineral which makes the components is replaced by another.[2] There is an important observation that McKie (1976) made, he categorized nyrereite into two different categories high and low nyrereite. There are two types because the Ol Doinyo Lengai lavas are very soluble when they come in contact with water or the atmosphere, the lava changes physically and chemically.[4] Therefore as nyerereite is at high temperature or warm we have what McKie (1976) calls high nyerereite but when it cools down and gets hydrated we have pirssonite that has a chemical formula of Na2Ca(CO3)2·2(H2O).[4]

[edit] Biographic Sketch

Nyerereite is part of carbonatites, which are igneous rocks that contain more than 50% carbonate minerals, they are usually found in volcanic dykes and sheets.[5] Nyerereite was first discovered by J.B. Dawson, between March 1960 and September 1965, the originality of the name came from Tanzania’s president, Julius K Nyerere.[2] Nyerere was the first Tanzanian to study at a British university, he attended the University of Edinburg where he obtained his masters degree in economics and history in 1952. He returned home and became a teacher and an active politician. A few years later he quit teaching to attempt to convince different leaders of Tanzania that independence from Britain would be a great advancement for the country. He then was appointed to persuade the British to grant the Tanzanian people their independence; a few years later Britain withdrew without aggression or violence. Nyerere became the first president to govern Tanzania in 1962, and implemented his social beliefs he acquired in Britain when he attended Edinburg University. In the end his socialist movement failed, and his policy of “community base farming” was unsuccessful. Julius Nyerere died on October 14, 1999. His people called him the teacher, and he himself often said he was a “school master by choice, politician by accident” (BCC News, 1999).

[edit] References

  1. ^ Webmineral data
  2. ^ a b c d Mckie, D., Frankis, E.J., (1976) Nyerereite: A new volcanic carbonate mineral from Ol Doinyo Lengai, Tanzania. Zeitschrift fur Kristallographie 145, 73-95
  3. ^ Hay, R.L., (1983) Carbonatitetuffs in the Laetolil Beds of Tanzania and the Kaiserstuhl in Germany. Contributions to Mineralogy and Petrology 82, 403-406
  4. ^ a b Zaitsev, A.N., Keller, J.,(2006) Mineralogical and chemical transformation of Ol Doinyo Lengai natrocarbonatites, Tanzania. Lithos 91, 191-207
  5. ^ Gittins, J., Jago, B.C., (1998) Differentiation of natrocarbonatite magma at Ol Doinyo Lengai volcano, Tanzania. Mineralogical magazine 62, 759-768
Languages