Final answer:
Diamonds and other precious gems are globally distributed by multinationals like DeBeers, with significant operations in South Africa, Botswana, Namibia, and Canada. Locally, countries rich in these resources, such as South Africa and Botswana, gain national wealth from mining, yet the profits often don't reach the miners. Sites like Ruggles Mine provide insight into the geological processes behind gem formation.
Step-by-step explanation:
The global and local distribution of important gem-bearing pegmatite districts varies geographically and is influenced by geological formations. Globally, significant diamond reserves and gemstone production operations are managed by large companies such as DeBeers, which has a significant presence in South Africa, Botswana, Namibia, and Canada. DeBeers controls a large portion of the global diamond production and maintains a worldwide distribution network for rough diamonds. Locally, various nations within gem-rich regions benefit differently from these resources. Places like South Africa's central gold and diamond-mining regions and Botswana's diamond mines show concentrated efforts in mining activities that contribute to national wealth and improve local standards of living.
However, despite the potential for economic benefit, it is noted that the wealth often fails to reach the hands who work in the mines, highlighting an issue with the distribution of wealth in the mining industry. Localities such as the aforementioned regions and Mozambique, which is known for its coal, participate in the extractive processes that lead to national revenue and improved living conditions, at least at a macro level.
The examination of geological sites such as the Ruggles Mine in New Hampshire, where a mafic di-ke cuts through granitic pegmatite indicates mining history and the processes involved in determining the age of rocks through the principle of cross-cutting relationships.