A few weeks ago I was wondering about the unusual rocks along a stretch of the Paugussett Trail in Monroe, even before I read the CFPA trail description that identified an old silver mine in that very spot. I took a look at the USGS bedrock geology map (click to enlarge) and learned there is a rock formation called the Straits Schist Basal Member, abbreviated Stb on the map and shown in orange. The Stb formation is defined as a gray schist with amphibolite, marble and quartzite and is known for containing metals.This is the same formation that pops up at Old Mine Park in Trumbull, location of a former Tungsten Mine. Back in the 1990's they were blasting nearby to build a corporate park and rock hounds were going in on the weekends to see what they could salvage of the metal-bearing rock (I collected a crate of rocks myself and will be using one for my first rock stash).


