Research into natural diamonds (figure 1) has emerged over the last two decades as one of the keys to understanding the deep earth.
Analytical advances, improved geologic knowledge, and the emergence of new diamond-producing regions (such as the Slave craton of Canada) have all contributed to this change.
While these pressure-temperature conditions seem extreme, for a large rocky planet such as ours, they are not.
The crustal age/craton basemap is from Pearson and Wittig (2008). (2009), Harte (2010), Harte and Richardson (2011), Tappert and Tappert (2011), Dobrzhinetskaya (2012), and the authors.
Localities are as follows: (1) Diavik, Ekati, Snap Lake, Jericho, Gahcho Kue, DO-27; (2) Fort a la Corne; (3) Buffalo Hills; (4) State Line; (5) Prairie Creek; (6) Wawa; (7) Victor; (8) Renard; (9) Guaniamo; (10) Juina/Sao Luis; (11) Arenapolis; (12) Coromandel, Abaete, Canasta; (13) Chapada Diamantina; (14) Boa Vista; (15) Koidu; (16) Kan Kan; (17) Akwatia; (18) Tortiya; (19) Aredor; (20) Bangui; (21) Mbuji-Mayi; (22) Camafuca, Cuango, Catoca; (23) Masvingo; (24) Mwadui; (25) Luderitz, Oranjemund, Namaqualand; (26) Orapa/Damtshaa, Letlhakane, Jwaneng, Finsch; (27) Murowa, Venetia, The Oaks, Marsfontein, Premier, Dokolwayo, Roberts Victor, Letseng-la-Terae, Jagersfontein, Koffiefontein, Monastery, Kimberley (Bultfontein, Kimberley, De Beers, Dutoitspan, Kamfersdam, Wesselton); (28) Kollur; (29) Majhgawan/Panna; (30) Momeik; (31) Theindaw; (32) Phuket; (33) West Kalimantan; (34) South Kalimantan; (35) Springfield Basin, Eurelia/Orroroo, Echunga; (36) Argyle, Ellendale, Bow River; (37) Merlin; (38) Copetown/Bingara; (39) Mengyin; (40) Fuxian; (41) Mir, 23rd Party Congress, Dachnaya, Internationalskaya, Nyurbinskaya; (42) Aykhal, Yubileynaya, Udachnaya, Zarnitsa, Sytykanskaya, Komsomolskaya; (43) Ural Mts.; (44) Arkhangelsk; (45) Kaavi-Kuopio; (46) W Alps; (47) Moldanubian; (48) Norway; (49) Rhodope; (50) Urals; (51) Kokchetav; (52) Qinling; (53) Dabie; (54) Sulu; (55) Kontum; (56) Java; (57) New England Fold Belt; (58) Canadian Cordillera; (59) Lappajärvi; (60); Ries; (61) Zapadnaya; (62) Popigai; (63) Sudbury; and (64) Chixculub. (2013), with permission of the Mineralogical Society of America. Plate tectonics is the modern unifying theory that explains the earth’s active geologic processes today, and is thought to have operated perhaps for as long as the latter half of the planet’s history.
No other planets in the solar system apparently have plate tectonics.
Even low elemental concentrations and minute features in diamond can now be analyzed using instruments with higher sensitivity and resolution.
As a result, study combining the inclusion and its diamond host is a powerful tool for geologic research, which itself has improved our understanding of diamond formation. These photos show inclusions of silicate minerals in natural diamond whose background reflectivity has been enhanced by faceting: almandine (left), magnified 10×; pyrope (center), magnified 40×; and diopside (right), magnified 30×. The purpose of this article is to describe our current understanding of where, how, when, and why natural diamonds have been formed.