Stop 10: CITY OF BALTIMORE POLICE HEADQUARTERS - 601 East Fayette Street
Continue walking east along Fayette Street to the Police Headquarters. This building and the pedestals for the flag poles are faced with “Rainbow Gneiss” (also known as Morton Gneiss) from Morton, Minnesota (Figures 10a and 10b).
This gneiss is about 3.6 billion years old, one of the oldest rocks in North America. The name is well suited for the contorted bands of black biotite mica, pink feldspar, and gray quartz. The polished finish highlights the grain and texture of this ancient and attractive Precambrian building stone.