Important iron ores
Hematite, limonite, magnetite and siderite
1. Iron ores and extraction of iron
2. Which one does the magnet pick?
Iron ores are not all the same. They come in different colours.
Pick the right answer
Predict: the four ores are crushed and mixed. A magnet passes over the pile. Which ore sticks to it?
- A. The blood-red ore
- B. The black ore
- C. The yellow ore
Explanation
The black ore is magnetite, the ore with magnetic properties, so it sticks to the magnet. Colour alone does not make a rock magnetic: the blood-red and yellow ores do not have magnetic properties.
3. 1) Hematite
| Ore | Hematite |
|---|---|
| Chemical name | Iron III oxide |
| Chemical formula | Fe2O3 |
| Properties | Blood red colour; more easily reduced |
| Iron % | 50-60 |
| Place of deposits | Oasis area (Western Desert) |
In iron III oxide, iron has oxidation state +3.
"Easily reduced" means the oxide easily loses its oxygen to give iron.
4. 2) Limonite
| Ore | Limonite |
|---|---|
| Chemical name | Hydrated iron III oxide |
| Chemical formula | 2Fe2O3.3H2O |
| Properties | Yellow hydrated oxide; easily reduced |
| Iron % | 20-60 |
| Place of deposits | Oasis area |
Same iron III oxide as hematite, plus water of crystallization: 3 H2O for every 2 Fe2O3.
True or false?
Limonite has no water in it.
Explanation
Limonite does contain water: the .3H2O in 2Fe2O3.3H2O is water of crystallization, so limonite is a hydrated iron III oxide.
5. 3) Magnetite
| Ore | Magnetite |
|---|---|
| Chemical name | Magnetic iron oxide |
| Chemical formula | Fe3O4 |
| Properties | Black ore having magnetic properties |
| Iron % | 45-70 |
| Place of deposits | Eastern Desert |
This is the ore the magnet picked out in the hook.
True or false?
Magnetite's formula is Fe2O3.
Explanation
Fe2O3 is the formula of hematite. Magnetite, the magnetic iron oxide, is Fe3O4.
6. 4) Siderite
| Ore | Siderite |
|---|---|
| Chemical name | Iron II carbonate |
| Chemical formula | FeCO3 |
| Properties | Yellowish grey colour; easily reduced |
| Iron % | 30-42 |
| Place of deposits | not given in the book |
Siderite is the odd one out: a carbonate, not an oxide. Here iron has oxidation state +2.
7. All four together
| Ore | lowest (%) | highest (%) |
|---|---|---|
| Hematite | 50 | 60 |
| Limonite | 20 | 60 |
| Magnetite | 45 | 70 |
| Siderite | 30 | 42 |
Match the pairs
Match each ore to its formula.
- Hematite
- Limonite
- Magnetite
- Siderite
8. Identify the ore
Pick the right answer
A geologist finds a black ore in the Eastern Desert. A magnet attracts it. What is its formula?
- A. Fe2O3
- B. Fe3O4
- C. FeCO3
- D. 2Fe2O3.3H2O
Explanation
A black ore from the Eastern Desert that a magnet attracts is magnetite, magnetic iron oxide: Fe3O4. Hematite (Fe2O3) is blood red, limonite (2Fe2O3.3H2O) is yellow and siderite (FeCO3) is yellowish grey.
True or false?
Siderite is an iron oxide, like the other three ores.
Explanation
Of the four ores, siderite is the carbonate one: its formula, FeCO3, contains the carbonate group CO3.
9. Sort the clues
Sort into groups
Sort each clue to its ore.
Blood red colourFormula with a water partYellow colourYellowish grey colourFound in the Eastern DesertContains the carbonate group
10. Summary
| Ore | Formula | Key clue | Iron % |
|---|---|---|---|
| Hematite | Fe2O3 | blood red; Oasis area (Western Desert) | 50-60 |
| Limonite | 2Fe2O3.3H2O | yellow, hydrated; Oasis area | 20-60 |
| Magnetite | Fe3O4 | black, magnetic; Eastern Desert | 45-70 |
| Siderite | FeCO3 | yellowish grey, a carbonate | 30-42 |
Can you explain why siderite is the odd one out?