By Sifelani Tsiko
THERE is need for more resources to be set aside for diamond mining research and exploration to enable geologist to try and trace where kimberlites which are a source of high quality gems lie in Zimbabwe, an expert says.

University of Zimbabwe geologist Nyikadzino Matura says that people involved in the Marange diamond rush, just before the area was sealed off, were only getting alluvial (or industrial) diamonds which are not of high grade as those found in a kimberlite.

"There is need for research and exploration to try and discover the kimberlite –the source of the diamonds which can hold deposits of high grade, gem quality diamonds," he says.

"As it is now in Marange, people are taking what is floating around as alluvial diamonds but they could be a chance that if a kimberlite is discovered in the area high quality gem diamonds can be found.

"This requires diamond experts and more resources to tap into the kimberlite. What has been found in Marange are the brown industrial diamonds," Mr Matura says.

No detailed studies on diamonds have been made in the Marange and most other parts of the country save for the few explorations by which were done by De Beers, Rio Tinto and SouthernEra Diamonds in Gokwe, the Zambezi Valley, central and southern parts of Zimbabwe.

According to geologists, a kimberlite is a type of rock best known for sometimes containing diamonds.
They say a kimberlite is an igneous rock composed of olivine, phlogopite, pyroxene and garnet, with a variety of chemically anomalous trace minerals.

Kimberlite occurs in the earth's crust in vertical structures known as kimberlite pipes. Kimberlite pipes are the most important source of mined diamonds today.

"In a kimberlite its possible to find a whole spectrum of diamonds from gem quality to industrial ones," says Mr Matura. "Its carrot shaped and can be found 150km deep in the earth's crust. It is derived from the mantle which is below the earth's surface."

He says kimberlites are usually found in areas which are stable, under very high pressure and high temperature conditions.

Other geologists say kimberlites are found as dikes and volcanic pipes which underlie and are the source for rare and relatively small explosive volcanoes.

Kimberlite pipes, they say, are the result of explosive diatreme volcanism from very deep mantle derived sources. These volcanic explosions produce vertical columns of rock that rise from deep magma reservoirs.

The morphology of kimberlite pipes are varied but generally include a sheeted dyke complex of tabular, vertically dipping feeder dykes in the root of the pipe which extend down to the mantle.

The diameter of a kimberlite pipe at the surface is typically a few hundred meters to a kilometre.
Many kimberlite pipes are believed to have formed about 70 to 150 million years ago, but in Southern Africa, there are several formed between 60 to 1600 million years ago (Roger Howard Mitchell - Kimberlites, Orangeites, and Related Rocks)

In Zimbabwe, Mr Matura says, diamonds can be found anywhere since almost three-quarters of the country's total surface area lies on what is known as the 'Zimbabwe Archaean Craton' which is very stable and conducive for the deposit of kimberlites.

It stretches from north-east, to the central and eastern parts of Zimbabwe down to the south and western parts of the country extending into Botswana which also has vast deposits of diamonds.

The border between Zimbabwe and Botswana forms what is referred to as the 'Orapa Kimberlite Track' which extends from Botswana into Zimbabwe.

This Track is the area in which there are some of the world's largest diamond mines –the De Beers owned Orapa and Lethlekane diamond mines in Botswana. The mines produce about 17 million carats per year.

In 1995, international diamond prospecting giant SouthernEra Diamonds entered into a multi-billion dollar venture with a local mining concern Rockover Resources Limited to carry out explorations in Tsholotsho, a district, in western Zimbabwe which also lies in the Orapa Kimberlite Track.  A total of 21 EPOs were granted for the Tsholotsho project which covers more than 14 000 square kilometres.

"The Government should support mining research in the country. We have the minerals and we need more resources to carry out studies so that we can full exploit the minerals," Mr Matura says.

"You need very good diamond geologists to work backwards to the source of the kimberlite in Marange. Diamond mining is a very costly and capital intensive venture which requires real expertise. At present we have few diamond experts if any in Zimbabwe," he says.

The major hurdles in diamond mining, he says, revolve around, capital, machinery, cost of exploration and exploitation, grading and more importantly marketing which is controlled by a handful of players in the diamond industry.

In addition, he says, the Government has to grapple with environmental impact assessments which are now a critical component of every major mining venture.

"All this requires expertise. There has been a lot of exploration in Zimbabwe and we don't know what these major mining houses are finding. It's a highly secretive industry which is sensitive and has stringent requirements," Mr Matura says.

"Mining is a costly business and exploration can take 10-15 years before actual mineral exploitation takes place or before a mining entity realises profits from mining."

"You need expertise to determine the exploitation rate, the reserves, to predict the prices and other factors in this diamond business. Its very expensive."

In simple terms, he says, the gem quality of diamonds is determined by tripple 'Cs' –clarity or clearness, carats or grade and the colour of the diamonds.

Diamond exploration in Zimbabwe dates back to the 1903 when alluvial diamonds were discovered  followed by the discovery of the first diamond kimberlite pipe in 1907.

In the early 1980s and 1990s a number of mining giants were granted exclusive prospecting orders (EPOs) for diamond search.

In 1995, UK-based Reunion in a joint venture exploration programme with a Canadian company, Argosy Mining Corporation discovered three small macro-diamonds near Lake Kariba.

Statistics in that year also indicated that diamond sales by the Mineral Marketing Corporation of Zimbabwe shot up to 240 000 carats from 123 000 carats in 1994.

Over the years the government revoked the EPOs for multinationals saying the companies were sitting on these vast claims blocking the participation of local companies and others in the exploration of precious minerals.

Some of the multinationals were accused of using EPOs to raise money on the international stock exchange when there was no actual work being done to exploit the claims. Some held over 20 000 claims each for over 20 years.

In the 1990s, Rio Tinto discovered three kimberlites in the Murowa area, about 40km from Zvishavane while Kimberlite Searches a subsidiary of De Beers discovered diamonds in areas around Bulawayo.

The Murowa reserve is estimated at 16,5 million tonnes of kimberlites at a grade of 0,9 carats per tonne. It was estimated that at least 500 000 tonnes of kimberlites would be mined every year from the mine

By 2000, about 463 diamond EPOs were issued and prospects were bright that more diamond deposits would be discovered if the explorations continued.

The first diamond discovery was made by De Beers at River Ranch in Beitbridge in the 1970s. Mining of the deposit could not take off because of the war. Zimbabwe's first diamond mine, the River Ranch began its operations in the early 1990s.

Africa is the largest producer of diamonds accounting for more than 50 percent of global production.
By 2004, the continent produced over 75 percent of the world's diamonds, with more than 1,9 billion carats worth more than US$158 billion having been produced.

The major producers of diamonds in Africa include Ghana, Tanzania, Angola, DRC, Namibia while Botswana and South Africa are the world's gem quality diamond producers.

De Beers controls about 70 percent of the world diamond trade by what experts say, stockpiling tough diamonds and limiting the amount sold.

There is growing pressure from African governments to bring value addition to the producing countries where diamonds are mined to create jobs and generate more foreign currency.

And, the diamond rush in Marange like the one that happened in the 1990s, has re-awakened Zimbabweans to the sensitive and highly controlled world of diamond trade.