Mystery Rock #2

Earlier this month I posted pictures of a mystery rock that were sent to me by one of my blog readers. On Friday I received an email from someone who had been directed to my blog from the Skeptics Guide to the Universe Forum. A friend of this person had found an interesting rock in a rock wall in El Paso, Texas and wanted to know if anyone could identify this rock. Below are some pictures of beautiful Mystery Rock #2:

Mystery Rock #2, Photo 1.

Mystery Rock

Mystery Rock, Photo 1.

A few weeks ago a blog reader named Bob wrote me to ask if I could help identify a "mystery rock" in his backyard. Bob sent me several photos of the rock and wrote:

Hi Evelyn,

I'm reasonably sure I'm wasting your valuable time with these "silly"
rock pictures, but I've been searching the web for similar pictures or
descriptions with no real satisfaction.

I am a computer tech by trade and know nothing about rocks.

I found this one unique looking rock on my property in Bergen County NJ.
It was one of I'm sure tens of thousands in a large rock wall that is at
least more than 75 years old. (It could be much older.)
I have seen none else that look like this one so far.

To keep this email short, here is my question:
Should I be more curious about this rock or just place it in a garden
bed for decoration?
 
Thank you very much for humoring me on this.
Bob.

Well, as a geologist I like nothing better than puzzling over an interesting rock-- so, Bob, you're not wasting my time at all!