A small site at the start of a brook - Harvard, MA

You step off the road in Harvard and more or less expect to find rock piles. There was a patch of woods I never explored, along Rt 111, so I stepped into the woods there last weekend and went downhill, past signs this was an old farm or orchard, down to the edge of a wetland. My feet found the first rock pile and, looking around to see if it was isolated, I saw a couple of others. Then I noticed an interesting configuration of wall, rock-on-rock, and rock pile - all in a line.

It was something like this:
This shows a portion of a stone wall at the top of the picture, a rock-on-rock, a rock pile, and the brook/wetland flowing off to the right. I left out some small boulders that are also in the line.

Here is a first pile, found by my feet: a rough oval, including a piece of quartz or quartzite:
Here is a closeup of the quartz:
There were a few other inconspicuous piles nearby, I might easily have missed them.

The main thing that caught my eye was a rock-on-rock next to the beginning of the brook.
I got the impression that the larger boulders in the brook were in a line with this rock-on-rock and, as I looked along the line, I could make out a break in the stone wall. Something prompted me to look behind me along the same line. There, hidden in the vines was a more substantial rock pile:Of interest, was the reddish burnt looking rock in the pile.
But what was most interesting was when I went to take a closer look at the rock-on-rock and found it was made of quartz.
This is quite rare and I can only think of two other places where I have seen quartz used in a rock-on-rock. One was at the end of a line of rock piles (not more than a mile from this current spot) the other was also associated with an alignment.

Following the same line over to the stone wall, there was a break in the stone wall and another piece of quartz:The next picture (sorry for the blurring) shows the whole line, with the stone wall in the foreground, the rock-on-rock behind it, then another boulder in the brook, and the larger rock pile is behind that in the same line: