Tanzania explains sharp diamond production drop in late 2025, blames rains and mining adjustments

Data from the Bank of Tanzania (BoT) show that diamond output fell to 43,244 carats valued at $6.1 million in the quarter ending December 2025. This was a steep fall from 111,125.8 carats worth $17.4 million recorded in the preceding quarter.

The figures indicate a 61 percent decline in production volume and a 65 percent drop in value within a three-month period.

The fall reversed gains recorded earlier in the year. During the first quarter ending March 2025, Tanzania produced 93,557 carats valued at $15.7 million. Production slipped slightly in the second quarter to 79,524.9 carats worth $14.4 million. Output then rebounded strongly in the third quarter to 111,125.8 carats, marking the highest quarterly level recorded since 2023.

However, the sharp decline in the final quarter raised concerns within the mining sector and among policy observers. Questions emerged about whether Tanzania’s diamond industry, though relatively small compared with gold and other minerals, was beginning to face deeper structural challenges. A senior geologist at the Ministry of Minerals, Mr Joseph Matalu, said the decline was largely the result of temporary operational and environmental factors rather than any long-term deterioration in the country’s diamond reserves.

“It is true that production declined in December 2025,” Mr Matalu told The Citizen. “The main causes were normal operational and environmental conditions, particularly the rainy season and production adjustments in certain mining areas.”

According to him, heavy rains during the period led to flooding in several small-scale mining pits, slowing extraction activities.

In addition, some pits, including those located in the Mwampangabule area, were temporarily suspended to allow for safety improvements and technical upgrades.

“Safety considerations are paramount in mining operations,” Mr Matalu explained. “Some pits had to be halted temporarily so that improvements could be implemented before activities resumed.”

He added that fluctuations in global diamond prices also played a role in influencing the behaviour of some small-scale miners. When international prices weaken, smaller operators often scale down production as a risk-management strategy.

However, he stressed that operational disruptions remained the primary driver of the fourth-quarter decline.

Williamson operations

Through the Ministry of Minerals, Williamson Diamond Limited, Tanzania’s principal diamond producer, also addressed the fall in output.

The company said the decline was linked to planned operational activities at its mine.

During the period, the mine was undertaking extensive waste rock stripping, a process that involves removing layers of non-valuable material covering diamond-bearing ore.

At the same time, the company relied on lower-grade stockpiles while preparing to access richer ore zones. “These activities are aimed at unlocking higher-grade areas for sustainable production,” the company said in a statement.

It emphasised that the decline in output was temporary and tied to technical requirements, safety considerations and the normal cycle of open-pit mining operations rather than a structural downturn.

Mining experts note that waste stripping is a capital-intensive but necessary process in open-pit mining. While it can reduce production in the short term, it is essential for maintaining long-term productivity.

The slowdown also coincided with a challenging period for the global natural diamond industry.

Industry data indicate that polished diamond prices remained under pressure throughout 2025. The weakness was largely driven by oversupply and intensifying competition from laboratory-grown diamonds.

According to Rapaport, the RapNet Diamond Index for one-carat stones fell by 9.9 percent during the year. Prices for smaller stones dropped even more sharply.

Market analysts also report that prices of lab-grown diamonds have declined significantly due to increased supply from major manufacturing hubs such as China and India.

The rapid growth of the lab-grown segment has continued to exert pressure on the traditional natural diamond market.

For relatively small producers such as Tanzania, whose share of global diamond supply remains limited, such market shifts can quickly affect export earnings when production also declines.

Recovery strategy

The Ministry of Minerals says it has begun implementing measures aimed at stabilising diamond production and protecting government revenues during 2026.

These efforts include strengthening supervision of small-scale mining operations and accelerating rehabilitation of pits affected by heavy rains.

Authorities are also intensifying inspections through the Mining Commission to ensure compliance with safety and operational standards.

Another priority is the completion of waste stripping activities at the Williamson mine. This work is expected to open access to higher-grade ore zones by the second quarter of 2026, which officials believe could significantly boost output.

In addition, the government is encouraging mining operators to adopt more cost-efficient technologies to help cushion them against global price volatility.