Diamonds in the Chapada Diamantina – Bahia, Brazil

Just before starting a new trip to Brazil (into manganese mineral deposits in Goiás and Minas Gerais), this is a new photogallery for a 2004 road trip aimed at learning about the Bahia diamond deposits (geology, formation, history, social and natural settings). Of course, it was just the perfect pretext for four old friends getting into another Brazilian road trip. It took us from Diamantina (Minas Gerais) to Andaraí and Lencóis (Bahia).
I just hope the new trip’s photos won’t take 10 years to be published…
Brasil Diamantina Andarai Lençois 2004 03 097


Lucapa Diamond Company Limited (ASX: LOM) (“Lucapa” or the “Company”) is preparing to commence the next phase of the the Company’s kimberlite exploration program at the Lulo Diamond Concession in Angola. New program includes extensive further evaluation of four known diamond-bearing Lulo kimberlites as Lucapa steps up its search for the sources of the exceptional alluvial diamonds being mined at Lulo. – March 23, 2015 ASX Announcement.


  • More than 80 kimberlite targets to be sampled and/or drilled at Lulo as part of a comprehensive 24-month program which builds on the positive kimberlite exploration results achieved to date.
  • New program to commence in April with extensive further evaluation of four known diamond- bearing pipes at Lulo and laboratory analysis of drill core.
  • First bulk samples also to be excavated from the priority L46 kimberlite, which has been identified as a likely source of the high-grade diamonds recovered from the E46 alluvial area at Lulo.
  • Program includes drilling of 48 priority targets in the western kimberlite province and first testing of 38 targets in the new eastern kimberlite province at Lulo.
  • Kimberlite program will utilise the original 10tph diamond sampling plant at Lulo to enable continuous alluvial diamond mining through main 150tph diamond plant.

You may get the full ASX announcement here: Lucapa-Steps-Up-Kimberlite-Diamond-Program-At-Lulo.

Pink diamonds – new research findings

Coloured diamonds attract a lot of attention nowadays – the post I have written a week ago based on a photo with coloured rough diamonds in a (Bahia?) Brazilian parcel attained record views on this blog and comments on Linkedin and Facebook.

For those professional gemologists addicted (or just mildly interested) in pink – red diamonds I have just come across an interesting article on the subject (just publicised by Tracey Greenstein in Linkedin).

Chromism-in-pink-diamonds, by John Chapman of Rio Tinto Diamonds and published in The Australian Gemmologist (Fourth Quarter 2014, Vol 25 – Number 8). The article is well written and discusses temporary color fluctuations either result of the polishing process, high temperature or illumination by short wavelength light of high intensity.These fluctuations are relatively short-lived. The author summarises his findings in the article’s first section:

Pink diamonds from Argyle have been known by polishers, laboratories and traders to exhibit a phenomenon of photochromism whereby their colour can be influenced by illumination of different lights and intensities. The influences are relatively short-lived and most conspicuous after illumination by short wavelength light of high intensity. This effect is particularly noticeable when using instruments to observe fluorescence, such as DiamondView, which after use with Argyle pink diamonds results in a distinctively bleached or pale colouration. Intensification of the colour can be achieved by subjecting pink diamonds to elevated temperature – thermo-chromism, while the colour can also change unpredictably during polishing – a phenomenon known as tribo-chromism. All these possible changes are temporary and the colour can be readily returned to an ‘ambient resting colour’.

Reference to pink diamonds in this article applies primarily to Argyle pink diamonds (Figure 1) rather than Golconda-style Type II pinks or type I purplish colours from Siberia or Canada.

Better read the full article (pdf in link above or at The Fancy Colour Research Foundation website) .

Minas de carvão do Pejão – Pejão coal mines (NW Portugal)

Na mina do Pejão: A melhor turma de Minas do Técnico em viagem (ou como agora se diria, on tour) com o Prof. Décio Tadeu e Prof. Diogo Pinto

Na mina do Pejão, 1986: A melhor turma de Minas do Técnico em viagem (ou como agora se diria, on tour) com o Prof. Décio Tadeu e Prof. Diogo Pinto

Meanwhile closed, the coal Pejão mine was for decades one of the most important Portuguese mines (employing over 3.000 workers in its heyday).
The main sectors of Minas do Pejão are the Couto Mineiro do Pejão and the Paraduça 1 claim, defining a corridor extending from Germunde to Paraduça – including Pedorido, Raiva e Paraíso, all in the Castelo de Paiva municipality (Aveiro district).
The main mining center is located 45 km by road E of Oporto, in the left bank of the Douro River. The Estrada Marginal (the panoramic road) passing in the right bank connects Oporto with Entre-os-Rios (in the confluence to the Douro and Tâmega rivers).
Like the S. Pedro da Cova, Pederneira, Lomba and other coal mines, Pejão is located within the Douro Coal Basin (Bacia Carbonífera do Douro) – extending from Esposende to Gafanhão and Queiriga (Castro Daire municipality).
in MACHADO, A. Cabral D. (1970) — As Minas de Carvão do Pejão (complete article here) – in Portuguese.
Entretanto já encerrada, a mina do Pejão, produtora de carvão, foi durante décadas uma das grande minas portuguesas (tendo empregue a dada altura mais de 3.000 trabalhadores).
Os principais compartimentos das Minas do Pejão, ou seja, o Couto Mineiro do Pejão e a concessão de Paraduça 1, ocupam uma faixa que se estende desde Germunde até Paraduça, passando pelas freguesias de Pedorido, Raiva e Paraíso, todas elas pertencentes ao concelho de Castelo de Paiva e distrito de Aveiro.
O seu centro principal de extracção e instalações situa-se em Germunde, na margem esquerda do Douro, e dista do Porto, por estrada, cerca de 45 quilómetros.
Na sua frente e do outro lado deste rio, de beleza e grandiosidade incomparáveis, passa a Estrada Marginal, por assim dizer uma estrada turística, que liga o velho burgo do Porto com Entre-os-Rios, situado na confluência do Douro com o Tâmega.
Estas minas estão situadas, como as de S. Pedro da Cova, Pederneira, Lomba e outras, na mancha carbonífera do Noroeste de Portugal, também conhecida por Bacia Carbonífera do Douro, que se estende aproximadamente desde Esposende até Gafanhão e Queiriga (no concelho de Castro Daire).

in MACHADO, A. Cabral D. (1970) — As Minas de Carvão do Pejão (artigo completo aqui).

Safe and sustainable mining with ISO standards

Mining is a temporary activity, with mines operating from anywhere between a few years and a few decades. Increasingly, however, what happens after a mine is closed, and the impact this has on the local community and environment, has an important influence on the competitiveness of the mining operation.
A new ISO subcommittee on mining reclamation management (ISO/TC 82/SC 7) has recently been created to develop International Standards that can help minimize the potential long-term damage from mining activities.
A mineração é uma actividade temporária, com períodos que variam, normalmente, de poucos anos a algumas décadas. Aquilo que acontece após o fecho da mina e o impacto que aquela decisão tem nas comunidades e ambiente locais tem, de forma crescente, um grand impacto na competitividade da operação mineira.
O reconhecimento daquele facto conduziu à criação de um novo subcomité ISO (ISO/TC 82/SC 7) para desenvolver Normas Internacionais que possam ajudar a minimizar o impacto de longo-prazo das actividades mineiras.

Best practices to adopt when a mine closes

Even though mining reclamation management is thoroughly done during operation, it is a general characteristic of mining reclamation that potential damages are observed for a long time after closing mines. And it is usual that a boosted regional economy due to the mining industry declines very rapidly after closing those mines and the region faces cavitations. According to experts:

The mining reclamation management must be supported by government and developers together and the opinions of local residents must be actively reflected in the process.

Government and mine operators must prepare measures for the control and monitoring of the environment, the utilization of closed mines, the activation of the regional economy, and the budget for the project at the time of closing the development.

Government and mine operators must prepare for the local residents, who could potentially be impacted by mine closings, an official communication channel to allow interaction between all stakeholders. For example, public hearings are a proven tool to ensure open communication.



GEMDiamondsGEM DIAMONDS just released their 2014 Full Year results.

You may obtain the report clicking here.

The company’s news release states that:

During 2014, Gem Diamonds demonstrated a strong operational performance, delivering on a number of strategic objectives, resulting in a robust financial position and maiden dividend. The Company continued to focus on enhancing operational efficiencies and investing in innovative technologies at both Letšeng and Ghaghoo, delivering improved earnings and positioning Gem Diamonds for long term sustainable growth.


  • Revenue US$271 million, up 27 %
  • Underlying EBITDA US$104 million, up 35 %
  • Attributable net profit US$33 million, up 57 
  • Basic EPS 24 US cents, up 57 %
  • Cash on hand US$111 million as at 31 December 2014 (net after debt); (US$99.4 million attributable to Gem Diamonds)



  • Carats recovered of 108 569
  • Average of US$2 540 per carat
  • Tonnes treated of 6.4 million
  • Waste tonnes moved of 19.8 million


  • The Phase 1 capital project has been completed on time and on budget
  • Final commissioning and optimisation of the plant is in progress
  • A total of 10 167 carats recovered during commissioning, (including a 20 carat white diamond, a 17 carat white diamond and a three carat orange diamond)


  • 5 US cents per share
  • Total dividend of US$6.9 million
  • Record date: 8 May 2015
  • Payment date: 9 June 2015

To read the news release in full, please click on the following link.