Hunting for rock piles, from southern Estabrook, over to Boaz Brown's

See map in previous post. A brook called "Dakins Brook" leads up past Farmer's Cliff and begins in a valley just shy of "Mink Pond". Please note this valley and the higher ground to the west which is where Boaz Brown's cellar hole is found (on a path 100 yards east of Hugh Cargill Rd.). That valley and land form have more rock piles sites than anywhere else in Concord. There are what I consider to be burial mounds up on the ridge (rectangular, more than 8 feet across, with hollows), and some very nice piles down in the valley, that are a bit unique. 
I have been to these places before but, even without that, exploring a ridge west of a headwaters is a good hunting strategy. Last Sunday, I wanted to take a walk near home, and went out with my wife, and followed that strategy, around the edges of the open "private" land and roads. So I ended up walking along the edge of that ridge: I mean here:

We got up on the ridge slightly south of where the good stuff starts (not realizing where we were) and I saw a couple of structures that were new:

I cannot make out much from these. You will have to look quite closely to see how the above is slightly rectangular, with a space to the left of the larger rock (a "lazy 9". Below, you can see two hollows in the structure, but I do not trust it. It is so degenerate.

I guess they are older structures. Overall, there are about six mounds, possibly burials, up on that northern piece of the above map. 
Then we came to a "real" rock pile:

I started wondering if we were over at Boaz Brown's. We were. And there are all kinds of peculiar rock piles on bedrock, along with short stretches of stone wall. Enough to make you wonder, what was Boaz Brown up to?

Here are two holes, that must be the "cellars":

Since the above rock piles are rather unusual and in the context of a historic period home, it is easy to suppose they are not Indian and not ceremonial.

However the visibility into the undergrowth was very good. It was cloudy, these woods are sparse, and I spotted something new. This seems undeniably ceremonial. It is a triangle:

 And it has a white blaze:

 It is a light tan feldspar:

Triangular mounds are rare. I know one in Wayland and one in Sterling (the one in Wayland is bigger, likely different).

Here is the trail in from Hugh Cargill Rd:

The triangular mound is immediately to the left in the saplings. The cellar holes are a few steps later on the right, and the other piles continue to the left. So Boaz Brown was looking out at this triangular mound from his front door. He knew it was there.