[ Adventures to remote destinations ]
 
A field-trip to old and new gemstone deposits in Brazil

Dietmar Schwarz (Gubelin Gem Lab), Francisco Bank (Gebr. Bank, Idar-Oberstein) and Masashi Furuya (Japan Germany Gemmological Laboratory, Kofu) had the chance to visit several gem-producing localities in the Brazilian states of Paraiba, Rio Grande do Norte and Minas Gerais.

The border region of northern Paraìba and southern Rio Grande do Norte became known world-wide at the end of the eighties when tourmalines displaying a hitherto unknown spectrum of colours were discovered. Actually, these so-called "copper-manganese bearing elbaite tourmalines", which became famous as "Paraìba tourmalines" in the trade, are mined in Brazil at three different localities:
  1. The Sao Jose da Batalha mine near Salgadinho in the Paraiba state. Just now, two mining companies (Mineracao Heitorita and Parazul Mineracao) are working at this site where the first "Paraìba tourmalines" were found in 1987.
  2. The Quintos de Baixo mine
  3. The area known as Boqueirao which is now mined by the company Mineracao Terra Branca. Quintos de Baixo and Boqueirao are situated in the Rio Grande do Norte state.
Production at the three mining sites is regular, but it seems that the percentage of larger crystals or fragments (this means > 1 gr.) is only very small. Rough material yielding faceted stones of more than 10 ct is extremely rare.

In this context it is important to note that during the Hong Kong Fair in September 2005, W. Constantin Wild & Co. from Idar Oberstein informed in a press release that since May 2005 bright, vivacious tourmalines in a colour spectrum covering pastel pink, mauve-lavender, shocking pink-violet, and a pure, shining green have reached the gem market. The tourmalines presented in Hong Kong were all unheated and said to originate from the famous pegmatite localities in the Alto Ligonha region in Mozambique. The size of these stones ranged mostly from 0.5 to 4 ct. Meanwhile, faceted stones up to 25 ct are available. Greenish-blue and blue natural colours have been described also. On heating, the famous "electric blue" or "neon blue" shades can be obtained.

First tests carried out by different gem labs revealed that the gemmological-mineralogical properties of the copper-manganese bearing tourmalines from Mozambique are very close to those known from the "original Paraìba tourmalines" from the north-eastern states of Brazil. The Gübelin Gem Lab is now in the position to positively identify this material and to clearly distinguish it from tourmalines from Brazil and Nigeria. This is done mainly on the basis of the analysis of trace element chemistry.

In Minas Gerais, several mines in the Itabira-Nova era region could be visited. This area is famous especially for its deposits of emeralds, aquamarines and alexandrites. Just a few months ago, a new emerald mine has joined the traditional sites Belmont mine, Capoeirana and Pitera mine. The new deposit which is situated ca. 3-4 kilometres NW of the Belmont site, is mined by a company called "Mineracao Rocha". Production of the first few months is very promising in terms of quality and quantity. The gemmological-mineralogical properties of the new emeralds seem to be very similar to those observed in the stones from the Belmont, Capoeirana and Pitera sites. All four deposits are situated in the same "emerald belt".

The world-known Hematita alexandrite occurrence in Antonio Dias County is famous because it produced for several years large quantities of high-quality alexandrite originating from an alluvial site (also pieces of exceptional size). Two mining companies got the license to work in this deposit. One is still mining in the alluvial area (at this moment mining activities are practically set at hold). The company "Mineracao Alexandrita" is currently working the primary mineralisations in an underground operation. Production is regular but consists mostly of small crystals/fragments. Since Hematita - in terms of quality and volume - is still one of the main alexandrite producers in the world, the actual mining situation indicates that larger faceted stones (> 5 ct) will be more scarce in the future and prices are supposed to become higher.  
      
 




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