The gemstone deposits of Brazil: occurrences, production and economic impact

Resumen

This article gathers
together data on the occurrence, production and economic importance
of gem deposits in Brazil, including specific information on the
major deposits. Of the 100 or so different types of gemstones found
in the country, the most important in terms of production and/or
originality are tourmalines, topaz, opals, varieties of quartz
(agate, amethyst and citrine) and emeralds. Brazil is also one of
the only producers in the world of imperial topaz and Paraíba
tourmaline. The country also produces diamonds, rubies and sapphires
on a smaller scale. Gem production in Brazil is, for the most part,
carried out by prospectors and a handful of mining companies,
reducing the capacity of the government to control the production
and sale of gemstones. Another factor that tends to drive the
industry to operate outside the law is the high tax burden, which is
as high as 53% on the sale of jewelry and 25% on uncut or polished
stones. Owing to the geographical distribution of gemstone deposits
and the enormous size of the country, Brazil is divided into four
gem-producing areas. In the Northeast there are primarily deposits
of emerald, amethyst, citrine, hyaline quartz, elbaite, aquamarine,
garnet, morganite and opal. The Central region is characterized
primarily by emerald and diamond deposits, whereas in the South
deposits and occurrences of amethyst, citrine, agate and diamond are
found. The East is characterized mainly by the presence of gemstones
associated with pegmatites and hydrothermal veins, Plio-Pleistocene
sedimentary placer deposits and isolated concentrations of diamonds.
Gem production in Brazil mainly occurs in the states of Minas
Gerais, Bahia, Rio Grande do Sul, Mato Grosso and Goiás. The State
of Minas Gerais is the largest producer and exporter of gemstones in
the country and is responsible for 74% of the official production,
which includes imperial topaz, beryl, tourmaline, spondumene and
brazilianite. The State of Bahia produces mainly emeralds, amethyst
and aquamarines and is the second largest producer of uncut colored
stones after the State of Grande do Sul, which is one of the most
important producers in the world of two of these: namely agate and
amethyst. The State of Mato Grosso produces garnet, topaz, zircon,
diopside, varieties of quartz and tourmaline on a smaller scale. The
State of Goiás mainly produces emeralds, along with garnet, topaz,
quartz (citrine and amethyst) and tourmalines. Natural diamond
production is also significant in Goiás and Mato Grosso, where
diamonds have been being unearthed by prospectors since the
beginning of the 20th century. At present, the best prospects for
diamond production in these states are to be found in kimberlites.
Of the wide diversity of gems produced, some, such as the Paraíba
tourmalines and the opal from Piauí, are renowned around the world
for their originality and gemological properties.