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Additional Authors Are Gene E. Tolbert And Arthur E. Nelson.
The United States Geological Survey (USGS) is a scientific
organization created in 1879, and is part of the U.S. government.
Their scientists explore our environment and ecosystems, to
determine the natural dangers we are facing. The agency has over
10,000 employees that collect, monitor, and analyze data so that
they have a better understanding of our problems. The USGS is
dedicated to provide reliable, investigated information to enhance
and protect our quality of life. This is one of their memos.
Most of the niobium resources of Brazil occur as pyrochlore in
carbonatites within syenitic intrusives of Late Cretaceous to early
Tertiary age in western Minas Gerais and southeastern Goils. Minor
amounts of it are produced together with tantalum from
columbite-tantalite concentrates from pegmatites and placers
adjacent to them, in the Sao Joao del Rei district in south-central
Minas Gerais. All the niobium and tantalum produced in Brazil is
exported. The only pyrochlore mined is from the Barreiro
carbonatite deposit near Araxa in Minas Gerais where concentrates
and ferroniobium are produced. Exploration work for pyrochlore and
other mineral resources are being undertaken on other carbonatites,
particularly at Catalao I in southeast Goias and at Tapira and
Serra Negra in western Minas Gerais. Annual production and export
from the Barreiro deposit are about 8,000 metric tons of pyrochlore
concentrate containing about 60 percent Nb205 and about 2,700
metric tons of ferroniobium with 63 percent Nb2O5. The annual
production capacity of the Barreiro plant is 18,000 tons of
concentrate and 4,000 tons of ferroniobium. Ore reserves of the
Barreiro deposit in all categories are 380 million tons with
percent Nb2O5. Annual production of tantalite-columbite from the
Sao Joao del Rei district, most of which is exported to the United
States, is about 290 tons, of which about 79 percent is tantalite
and about percent is columbite. Reserves of tantalite-columbite in
the Sao Joao del Rei district are about 43,000 tons of proved and
73,000 tons of probable ore.
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