South Africa's Archean ultramafic lavas.
Some of the oldest chert in the world.
... of the Little Colorado River, near Leupp, Arizona.
Paleozoic sedimentary rocks atop Precambrian gneisses.
Lichen covers the slopes of a small cinder cone in southwestern Iceland. Taken from the rim of neighboring Grábrók.
... at Tigerton, Wisconsin. Zoom in to see the rapakivi texture of the feldspar. This rock unit is part of the 1.4 Ga Wolf River Batholith.
Ishpeming, Michigan. Locally known as "jaspilite".
... between Marquette and Negaunee, Michigan.
... featuring a billion+ year unconformity between Archean gneisses and Keweenawan basalts.
... near Wawa, Ontario. Google Street View: goo.gl/maps/bwMUXSJw1rQ2
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