Check out this South African City image:
Pegmatitic feldspathic orthopyroxenite (Merensky Reef, Bushveld Complex, mid-Paleoproterozoic, 2.054-2.055 Ga; Rustenburg Platinum Mine, northeastern South Africa)
Image by James St. John
Pegmatitic norite (4.8 cm across at its widest) from the Precambrian of South Africa.
LLIs are large layered igneous intrusions. Famous examples include Montana’s Stillwater Complex, southern Africa’s Great Dike of Rhodesia, the Muskox in Canada, the Dufek in Antarctica, Greenland’s Skaergaard Complex, and South Africa’s Bushveld Complex. LLIs consist of thick successions of ultramafic intrusive igneous rocks displaying small-scale to large-scale layering. The layering in LLIs is the result of crystal settling during cooling of the original magma. Repeated injections of magma is thought to be necessary in order to get layering throughout the extremely thick sections of rock. LLIs typically have economic concentrations of important metals (e.g., chromium, platinum).
This coarsely-crystalline rock is from a platinum mine in the 2.06 billion year old Bushveld Complex, an LLI in South Africa. It is a peridotite (= ultramafic, intrusive igneous rock) with pegmatitic texture (very large crystals) and is dominated by dark-colored orthopyroxene, plus some grayish plagioclase feldspar – pegmatitic feldspathic orthopyroxenite. There are scattered, non-platiniferous sulfides (see left of center, near the top of the large gray plagioclase) and small, scattered chromite grains (FeCr2O4).
Stratigraphy & age: Merensky Reef, uppermost Critical Zone, Rustenburg Layered Suite, Bushveld Complex, mid-Paleoproterozoic, 2.054-2.055 Ga
Locality: Level 17, Rustenburg Platinum Mine, northeastern North West Province, northwest of the city of Johannesburg, northeastern South Africa
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