The Lu-Enlilla archives, contemporary of Ibbi-Sin, king of the Third Dynasty of Ur, around 2000 BC, attests the existence of a regular trade between Ur and Magan (or Makkan). Other texts, from 2300 BC mention Magan as a producer of copper and diorite.
Some researchers have suggested that it was Oman:
Also, in ancient times, this region was producer of copper and diorite (Toshké) as shown, for example, a black diorite statue of Kephren:
Note that this black stone was also popular, around the same time, by Mesopotamian kings. Under Gudea, they called this diorite "stone Magan". The kings of Ur were importing this material and have build likewise life-size statues:
Kerma, the site of "Doukki Gel" was very extensive from the middle of the 3rd millennium BC. The Deffufa, built of mud bricks, is dated 2400 BC. The tombs of the time delivered a large number of manufactured objects attesting to a long-distance trade, with the development of copper metallurgy, bronze and craftsmanship in woodworking.
400 archaeological sites have been identified in the Dongola Basin. Some, like Kadrouka date back to Neolithic knowing copper.
In this region, no name is attested in the 3rd millennium. Even in the second, there is no evidence that the name "Kush" or "Kush" which appears in part of the 12th dynasty pharaoh was extended beyond the third cataract.
The name "Magan" may well have co-existed with that of "Kush" to the middle of the 2nd millennium BCE.
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My notes of veracity :
By "Magan", the Mesopotamians have designated the Horn of Africa: 2.5 / 5
By Magan, the Mesopotamians have designated a region of Iran: 2/5
By Magan, the Mesopotamians have designated the country of Oman: 2/5