Here is the iron(II) sulfate heptahydrate crystals which I made from steel nails. There were some other metals in those nails, so you can see impurities of different color (the green crystals are iron(II) sulfate heptahydrate).
Here is the iron(II) sulfate heptahydrate crystals which I made from steel nails. There were some other metals in those nails, so you can see impurities of different color (the green crystals are iron(II) sulfate heptahydrate).