Iron ehevkinite reported in this paper was discovered in a quartz syenite, which had intruded into Archaean marble, from a certain district in Hubei Province. It occurs as globular masses whose maximum weight can be a...Iron ehevkinite reported in this paper was discovered in a quartz syenite, which had intruded into Archaean marble, from a certain district in Hubei Province. It occurs as globular masses whose maximum weight can be as great as 1 kg. Iron ehevkinite has a black or pitch blaee color, with subconchoidal fracture. Specific gravity is 4.53±0.05. Microhardness 466.33-583.80kg/mm^2. Refractive index 2.02.It is metamiet, and the conversion temperature from metamiet state to erystallinity is 825℃. Chemical analyses give the following formula: (TR1/47Fe0.095^2+Th0.09Ca0.31U0.009Na0.11K0.01 Mn0.001)2.94(Ti1.44Fe0.57^3+Ta0.009Nb0.01)2.029(Si1.94Al0.06)2[O10.92(OH)1.05]12. It's chemical composition is characterized by a higher iron content (FeO+Fe2O3=17.58) in comparison with that in normal ehevkinite. Rare earth eontents, except for Ce, are also high, notably neodymium and lanthanum. The oxidation of Fe^2+ in iron chevkinite is caused by the water that had been subjected to irradiation and then found its way through fine cracks into the mineral The change in ionic radii involved in the oxidation of iron may be responsible for the metamietization of the mineral This interpretation accounts also for the eonstant association of a certain amount of water with metamiet minerals.展开更多
文摘Iron ehevkinite reported in this paper was discovered in a quartz syenite, which had intruded into Archaean marble, from a certain district in Hubei Province. It occurs as globular masses whose maximum weight can be as great as 1 kg. Iron ehevkinite has a black or pitch blaee color, with subconchoidal fracture. Specific gravity is 4.53±0.05. Microhardness 466.33-583.80kg/mm^2. Refractive index 2.02.It is metamiet, and the conversion temperature from metamiet state to erystallinity is 825℃. Chemical analyses give the following formula: (TR1/47Fe0.095^2+Th0.09Ca0.31U0.009Na0.11K0.01 Mn0.001)2.94(Ti1.44Fe0.57^3+Ta0.009Nb0.01)2.029(Si1.94Al0.06)2[O10.92(OH)1.05]12. It's chemical composition is characterized by a higher iron content (FeO+Fe2O3=17.58) in comparison with that in normal ehevkinite. Rare earth eontents, except for Ce, are also high, notably neodymium and lanthanum. The oxidation of Fe^2+ in iron chevkinite is caused by the water that had been subjected to irradiation and then found its way through fine cracks into the mineral The change in ionic radii involved in the oxidation of iron may be responsible for the metamietization of the mineral This interpretation accounts also for the eonstant association of a certain amount of water with metamiet minerals.
