(Al
and Ca). The Brazilian garnet is very rarely used as a gem. Certain
regions in the southern part of Minas Gerais, in the Northeast
(Paraiba and Rio Grande do Norte) and along the coast of Baia and
Espirito Santo, have sold almandite for use as abrasives.
Almandite
appears generally in mica schists and gneisses and in their alluviums.
Pyropes are found in the alluviums of the Triangulo Mineiro (wes-; tern Minas Gerais). Spessarite is found in the region of Lafayete in Minas Gerais.
TOPAZES
This is a fluorine aluminum silicate of hardness 8, density of 3.4 to 3.6 and average index of refraction of 1.162. It occurs principally in prisms and is colorless or wine-yellow, blue or pink.
The
most valuable is the topazine colored stone and at times, is priced
from 10 milreis to 300 milreis a carat. In Brazil it is found in Ouro
Preto,; P.odrigo Silva, Dom Bosco and in Salinas all in the state of
Minas Gerais.
Minas
Novas, also in the state of Minas Gerais produces blue topazes, as does
Teofilo Otoni. Salinas and, Teofilo Otoni produce hyaline or
transparent topazes. Blue or rose topazes vary between 1Q milreis and
400 milreis a carat in price, and the hyaline, between 10 and 25
milreis.
In Serra das Eguas and Ituassu (Baia) the topaz is found sporadic-: ally associated with the emerald.
TOURMALINES
This
is another stone which has brought fame to the northeastern part of
Minas Gerais. It is an aluminum borosilicate of green, red, black or
sapphire blue color. Its hardness varies from 7.0 to 7.5 and its
density from 2.98 to 3.25. The average refraction index is 1.63. It
occurs in short or elongated prisms, sometimes of two colors, red in
the center and green outside.
In Minas Gerais, the tourmaline is found in Salinas, Arassuai, Teo- filo
Otoni, Itamarandiba, Minas Novas, Lajao, etc., associated with quartz
in veins of pegmatite. In other states it is found in the same places
as beryls but I is rarely fit to be used as a gem.
In 1940, tourmalines were priced at 3,000 milreis per kilogram.
BERYLS
This stone has been included in the section relative to Berryllium in the chapter on Metallic Minerals.
