Rattlesnake Hill - the other brook

When writing about Rattlesnake Hill, I recently commented that there was a 2nd brook cutting into the hill from the south (leading to Great Brook) which needed to be explored. Here then is the result of exploring a 2nd valley of the hill.

The larger blue outline is a typical "marker pile" site, built along outcrops:

This is a bit decrepit but good reason to equate it with the many other marker pile sites, found up and down this valley of Beaver Brook/Elizabeth Brook - the valley of Rt 495. Every hill nearby has these (multiple) types of sites.

 

But I look at this photo and see something else:

There is a distinct pathway running up the right-of-center of the picture. This may be a "pathway" site rather than a marker pile site - where the pile guide a person along the path.

***

Across the valley, about where indicated by the smaller blue outline on the map, was somthing quite a lot rarer: a substantial triangular pile. Seen from each corner:

I cannot escape the impression that there is a small superficial "hollow" in the center of the last picture, opening to the right. This pile, as well as the small one in the background (last photo) have chunks of quartz:

This shaped pile is not common and the other example I can think of (southern end of Hycrest pond in Sterling) is not similar enough to claim a relationship.
Again, a success finding piles by going to the top  of a brook connected to a navigable waterway.