Crystals, but not ice

The largest of these tiny crystals is maybe half an inch tall - can't for the life of me remember if they are Quartz crystals or something else. I think they came from one of the mines in India, many years ago. Feels a little strange to be posting this kind of crystal at this time of the year - normally, I would be posting ice crystals from an overnight frost! Not as sharp as I wanted, but it was a heavily overcast day yesterday (with a weather advisory in effect), and there was absolutely no light in my place.