Here is a massive outcrop of Scituate granite.
Here are the foliations of this rock
Some of this stone was used to build a slanted slab wall that is nearby.
Here's a gravestone made of foliated granite in a local farm cemetery. It is also extensively split. This type of granite was not used often in grave markers, probably for this reason.
With more examples for comparison, it may be possible to estimate how long these eroded manitous have been standing in place.
Many of the standing slabs and manitous I have photographed over the years are thicker than these, often up to 6 inches. I will write about them in a later post. Maybe there once were many more thin manitous, but they have slowly eroded and broken.