This photo comes from my field work in 1999. It is in the top 5 cool geology pictures I have. Though the picture quality sucks, the geologic principal is stellar.
The rock is a pelitic schist. The two veins are quartz.
The interesting things to note are that one quartz vein (down from upper left to lower right) is pretty much unchanged. This represents a 'zone of flattening'.
The other quartz vein (the squiggly one; down from upper right to lower left) is within a 'zone of compression'. It demonstrates the direction of compression oriented between approximately N18-40 E.
Which fits in with the regional geology of south western Maine very well.
Teachers, feel free to use in class. Questions? Comments?