Polished slice of impact breccia from the Black Member of the Onaping Formation, Sudbury Basin. The specimen shows angular lithic clasts of target rock suspended in a dense black pseudotachylite melt matrix. Notable feature is a flow-banded zone of rare blue impact melt glass, visible as pale blue to gray-blue schlieren with swirled texture.
This is from an old collection. My accession number 072655 is on blue tape; you may easily remove it if you so desire.
The blue color reflects shock-melted, silica-rich target material and is uncommon in Onaping material, which is typically black to dark gray. Thin cut displays both matrix and clasts clearly. No repairs.
Significance:
The Onaping Formation represents fallback breccia deposited immediately after the 1.85 billion-year-old Sudbury impact event. The black pseudotachylite formed by frictional melting during crater formation.
Blue melt phases like this are sought after by collectors for their aesthetic contrast and petrologic interest.
The last photo is a false color LiDAR map of the Sudbury Basin and the 8 km (5 mile) diameter Wanapitei Lake, remarkably enough, a second impact crater that formed relatively recently, 1.8 billion years after the Sudbury structure.
(This is the only known place on Earth with two adjacent impact craters separated in time this way.)
Great for impactite, meteorite, and Canadian geology collections. Old stock, no longer collected in the mines. See photos for exact specimen you will receive.
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