Unlikely that it was ground. The detail photograph shows what could be
errailleur scars around the point of percussion. Perhaps someone took a
punch, placed it at regular intervals around the edge of the back of the
mirror, and gave it a light tap with a hammer. Not the removal of material
at the small end of each cone, which are clearly blown out, not ground.
Glass like that can have high internal consistency, making it relatively
easy to flake in a predictable manner. I've knapped projectile points from
it back in my undergrad, and it works beautifully, though the dust from it
will cut your hands to ribbons. Can't help with the name, but look at each
flake as basically one half of a BB hole in the window of your local fast
food joint.

Scarred,
CGCD