Cerdito Prospect Rift Crystals

Crystals of the North American Rift

A very unique new discovery. While prospecting in the wilderness of Ontario a few years ago we discovered this incredible site. It contains very graphic and real evidence of the ancient Midcontinent Rift, a major North American geologic event that occurred about 1.1 billion years ago in the Lake Superior region. At that time, east and west North America were separating from each other. The continent nearly split in half along the Midcontinent Rift, a bow-shaped crustal divergence which extended from northeast Kansas, arcing through the present-day Lake Superior Basin and angling southeast through Michigan. As this happened major faults and fracture zones formed in the host rock of the crust. Here the matrix rock is Rove Formation, which was laid down as fine clay-rich sediment in a deep water basin and hardened into rock before the rifting occurred. During the rift formation the crust was tearing apart and the Rove sediments became heavily fractured. The resulting cavities infilled with quartz minerals, including amethyst, smokey quartz, citrine, and clear crystal – sometimes all in the same piece! For reasons unknown, after about 20 million years the rift failed and spreading stopped. A billion years later, Ice Age glaciers carved out the old fracture zones of the rift valleys, resulting in Lake Superior’s unique boomerang shape today. We dug into this strange site and discovered some places along the quartz veins where the minerals did not completely fill the cavities. In these places crystal terminations are evident. There are very few of these and they are presented here for the very first time. This Pacific GeoLab site is the only location where evidence of the Midcontinent Rift event is preserved in such vivid and beautiful detail.

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To see this site and get a feel for our excavation here, see our expedition video: “Cerdito Prospect”