Interesting Little Rock/Mineral With Glass-Like Sections

I've had this rock in a display cabinet for ages, not sure where I got it, possibly from a local flea market, I often wondered what type of rock it is. It has smooth glass-like sections on several sides, not including the cut & polished side obviously, & is partially translucent when a bright light is shone into it. It weighs 198g (approx. 6.98oz) on a regular digital kitchen scale.

Here's a link to some pictures, including one with a tape measure for scale.

https://www.dropbox.com/sh/n38n07yu10y3ub0/AABAgZ4SI39x3zmsB3D8nKlKa?dl=0#/