The production process must be very technical, but under magnification the glass is a mass of fine, parallel bundled rods, most likely a by-product of the fiberoptic cable industry.

I recollect when I first bought a few large cabochons of this material from some small Russian table in Tucson the cutter explained that it was military glass; likewise some guy in Idaho, as my faulty memory recalls, said the red-brown variant of the glass was used in tank turret lasers.