CH Pegmatite

Greenstone Flow
Greenstone Flow

The Greenstone flow can be traced from Houghton to Keystone Bay, and during its eastern extent it is more than 1000 feet thick. It is possible to see the pegmatitic interior portion of this flow in many places.  Along the fault-bound NW-SE trending slot SE of Lake Manganese are excellent outcrops that are easy to visit.

In this place you can see the distinctive texture of these basaltic pegmatites, which are exposed on weathered surfaces which are in the interior of the Greenstone, approximately 1/3 of the way from the top. It differs from all the other parts of the flow by having plagioclase crystals, usually an off white color, which stand out clearly and form grouped aggregates. They appear like ancient writing to many observers, but they likely represent an arrangement during their dendritic crystallization somewhat like snowflakes. Some outcrop photos are below.

10 cm