The best African country for buying diamonds depends on factors like the quality of diamonds, pricing, and the legalities involved in purchasing. Here are a few key countries known for their diamond industries:

1. Botswana: Botswana is one of the largest producers of high-quality diamonds in the world. The country has a reputation for ethical mining practices, and its diamonds are highly regarded for their quality. The government also has a strong control over the diamond industry, making it relatively safe for buyers.
2. South Africa: South Africa is historically known for its diamond mines, such as those in Kimberley. While production has decreased in recent years, the country remains a significant player in the diamond market. South Africa also has established regulations to ensure diamond authenticity.
3. Namibia: Namibia has a rich supply of diamonds, particularly along its Atlantic coastline. The country is known for its high-quality diamonds, and many of them are ethically sourced. Namibia also follows international certification protocols, ensuring legitimacy.
4. Angola: Angola is one of the largest diamond producers in Africa, with several high-quality mines. However, the industry here can be less transparent and may involve more complex legalities for buyers.
5. Zimbabwe: Zimbabwe has diamond resources, especially in the Marange region. However, the diamond trade here can sometimes be murky due to political and human rights concerns, making it a less straightforward option for ethical buyers.

If you’re looking for both ethical sourcing and high-quality diamonds, Botswana and Namibia are likely your safest and best options. Always ensure to buy from reputable sources and inquire about certification to avoid conflict diamonds.