I recently received a beautiful rock and mineral collection that had been sitting in my aunt and uncles garage for the past decade or so. I came across this mineral and cannot figure out what it is. I don’t know where it is from. All I know is that it appeared to fizz very slightly in vinegar, is softer than 5 on the hardness scale, and the little crystals break off easily at maybe one or two fracture points. I’m leaning towards it being Dolomite right now, but what do you guys think? The little piece by it is the broken off piece that I just picked off with my finger, and the size comparison is a grape. Thank you!