GABORONE, Dec. 20 (Xinhua) -- Botswana's mining production index fell to 87.1 in the third quarter of 2018, posting a year-on-year contraction of 4.2 percent, triggered by the continued slowdown in the diamond mining sector, its statistics office said on Thursday.

In its latest index of the physical volume of mining production, Statistics Botswana announced that the main contributor to the decrease in the index was diamonds, having contributed 4.6 percentage points.

The quarter-on-quarter analysis shows a decrease of about 7 percent from the index of 94.0 during the second quarter of 2018 to 87.1 observed in the reference period, according to the latest figures.

According to the recently released statistics, the diamond production decreased by 4.8 percent during the third quarter of 2018, compared to the same quarter of the previous year.

"The decline came as a result of planned strategy to reduce bulky production in order to align production with trading conditions," said Burton Mguni, the southern African country's statistician general.

Mguni said the quarter-on-quarter analysis reflects that diamond production declined by 8.4 percent during the third quarter of 2018 compared to the second quarter of the same year.

Since the 2008 world credit crunch, Botswana has struggled to fully recover from the unfavorable trading conditions on the international market, as most buyers slowed down treating diamonds as luxury.