Looks like a Bennington but

[Newblue]

This doesn’t have the typical white mark a Bennington has. It is 17mm. Completely opaque. 

[Steph]

I agree with your reservations -- not a Bennington.  

Is your sense that it's a lighter or heavier marble?

 

From the pictures I'm leaning toward a newer, more dense clay than a Bennington would have.

[Newblue]

8 minutes ago, Steph said:

I agree with your reservations -- not a Bennington.  

Is your sense that it's a lighter or heavier marble?

 

From the pictures I'm leaning toward a newer, more dense clay than a Bennington would have.

I really know nothing about marbles, I’m just learning. I only know Bennington’s have that white mark and this doesn’t. 
It feels a little lighter than the other glass marbles of the same size. 

[Steph]

Lighter?

Could be normal clay, but it's larger than usual for basic "commie" ... the most common clay marbles.  

The shininess is also unusual for an older clay marble.  But that could mean little to no play wear, I suppose.  If it is common clay, then don't wash it.  I've had the colors come off when I washed clays.  

[akroorka]

I thought that it might be Lapis Lazuli.

Many of these came home with our Brave and Women and Men from Iraq and Afghanistan military service.

The little chip kind of dispels that.

Nice deep blue marble—I like it.

Marble—On!!

And much respect to those that have and are serving our country!!!!!!!!!!!!