Diamonds are found in kimberlite and lamproite pipes, which are volcanic structures that brought the diamonds to the surface from deep within the Earth's mantle.

Here's a more detailed breakdown:

* Kimberlite pipes: These are the most common source of diamonds. They are formed when magma from deep within the Earth's mantle erupts rapidly and violently to the surface.

* Lamproite pipes: These are less common than kimberlite pipes, but they can also contain diamonds. Lamproite magmas have a different chemical composition than kimberlite magmas, and they tend to be found in older geological terrains.

Here are some examples of major diamond-producing regions:

* Africa: South Africa, Botswana, Democratic Republic of Congo, Angola, Namibia

* Australia: Western Australia

* Russia: Siberia

* Canada: Northwest Territories, Nunavut

* Brazil: Minas Gerais

* India: Madhya Pradesh

* China: Shandong

* Venezuela: Bolívar State

Diamonds can also be found in alluvial deposits, which are formed by the erosion and transportation of kimberlite and lamproite pipes. These deposits are often located in riverbeds or beaches, and they can be a source of diamonds that have been transported long distances from their original source.