Magaliesberg, South africa
I couldn't decide how to characterize this specimen. It comes from a mine that produces the amethyst variety of "cactus quartz". However, it is quite dark, not the pretty violet-purple of amethyst. Close inspection shows that the large central crystal is a phantom - smoky quartz over amethyst. There is also an area of citrine (yellow-orange colored quartZ). In the end, I decided to just call it "quartz".