Botswana, the country with the biggest diamonds, gets an improved 10-year deal with miner De Beers

GABORONE, Botswana — The Botswana government signed a new diamond sales agreement crucial to its economy with the De Beers mining company on Tuesday after seven years of negotiations.

The deal gives the government an increasing share of diamond sales through the Debswana company — its joint venture with De Beers, a subsidiary of Anglo American.

Botswana, a sparsely populated and arid country in southern Africa, is the biggest producer of diamonds by value and the second biggest by volume behind Russia. Diamonds account for around 80% of Botswana’s exports and a quarter of its GDP, according to the International Monetary Fund.

But a decline in the price and demand for mined diamonds has badly hampered the Botswana economy and was a central issue in a national election last year. The party that had ruled for 58 years since independence from the British was voted out in a stunning result that was largely a reaction to new economic hardships related to the downturn in the diamond industry.

The new 10-year sales agreement gives the government a 30% share of Debswana’s sales up from 25% for the first five years and a 40% share for the following five years. There is an option for a five-year extension to the agreement, the two parties said, when the share of sales will be 50-50.