Both top and broken off bottom have distinctive natural faceting that make this a great collector's item. I can't find its more specific name after various Google searches. It's not like the spherical type that's more common.
"Old Collection" material - from a find that was quickly exhausted - many years ago. Hadn't seen anything like it, nor any since, and one thing I like about it is its resemblance to good quality Ruby. Red to pink color, these display pieces are quite nice.