I’ve never heard of it either.
Some years ago as the story is told, a drilling contractor was working on the erection of a TV tower to serve TB.
As the rock cuttings came to the surface, the drillers found large quantities of purple, glass like rock.
Realizing the site contained something valuable, an open pit was excavated and a massive ledge of amethyst, several feet thick, was discovered.
Today, there is a book store/rock shop and overlook area where visitors can buy chunks of the stuff for $1 Canadian per pound. There is also a rock shop in TB that sells polished curios and jewelry made from the stuff.