One off - Natural Iron Quartz cluster, Quartz with Iron. Origin Brazil. This one is 15cm x 9cm.
One off - You get the one you see here.
Iron Quartz, is essentially the same crystal as Amethyst and Citrine, they are all the same mix on minerals with the same chemical formula SiO₂. The difference of each is the rate of cooling process after the initial crystalisation process. The longer the mineral is hot, the more the colour changes from purple eventually to this almost colorless variety. If you look at the crystal formations, you can see they have the same features as Brazilian amethyst.