Recognizing hematite and magnetite iron ore involves a few key steps that focus on their physical and chemical properties. Here's how you can identify each:
Hematite (Fe2O3)
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Color and Appearance:
- Hematite typically exhibits a rich, rust-red to reddish-brown color.
- When polished, it can have a metallic silver appearance.
- The streak (the color of the powder produced by rubbing the mineral on a streak plate) is usually red or reddish-brown.
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Luster:
- Hematite can range from metallic to earthy, depending on its form.
- Specular hematite has a shiny, metallic luster, while earthy hematite looks more dull.
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Hardness:
- Hematite ranks about 5.5 to 6.5 on the Mohs hardness scale.
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Density:
- Hematite is relatively dense, with a specific gravity of approximately 5.3.
Magnetite (Fe3O4)
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Color and Appearance:
- Magnetite is typically black or a very dark grey.
- Its streak tends to be black as well.
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Luster:
- Magnetite has a metallic to sub-metallic luster.
- It looks shiny and can sometimes exhibit a dull black appearance if it is not well-polished.
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Magnetism:
- One of the distinguishing features of magnetite is its strong magnetic properties. Magnetite is naturally magnetic and will attract small iron objects.
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Hardness:
- Magnetite has a hardness of about 5.5 to 6.5 on the Mohs scale.
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Density:
- Magnetite is also dense, with a specific gravity of about 5.2, which is similar to hematite.
Additional Tips
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Field Tests:
- Use a magnet: Magnetite will attract a magnet, while hematite will not, unless it contains iron inclusions.
- Streak test: Rubbing the minerals on a streak plate to observe the color of the streak can help in identification.
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Location:
- Sometimes knowing the geographical location can provide clues, as certain types of iron ores are more prevalent in specific regions.
Both hematite and magnetite are important iron ores and can be identified through these methods. If unsure, laboratory analysis can provide definitive identification.
