The key difference between magnetite and hematite is that the iron in magnetite is in +2 and +3 oxidation states whereas, in hematite, it is only in +3 oxidation state.
Magnetite and hematite are minerals of iron. Both have iron in different oxidation states, and they are in the forms of iron oxides. Another important difference between magnetite and hematite is that the magnetite is black in colour, but hematite has a variety of colours.
CONTENTS
1. Overview and Key Difference
2. What is Magnetite
3. What is Hematite
4. Side by Side Comparison – Magnetite vs Hematite in Tabular Form
5. Summary
What is Magnetite?
Magnetite is an iron oxide with the chemical formula Fe3O4. Actually, it is a mixture of two iron oxides, FeO and Fe2O3. Therefore, we can show it as FeO·Fe2O3. According to the IUPAC nomenclature, its name is iron (II, III) oxide. But, commonly we name this as ferrous-ferric oxide. Magnetite got its name because it is a magnet.
Figure 01: Magnetite Appearance
Magnetite is black in colour, and its streak is also black. It has a metallic to dull lustre. On the Mohs scale, its hardness is given as 5.5 – 6.5. Magnetite has an octahedral crystal structure, but we can rarely see rhombododecahedron types. It shows an irregular, uneven fracture. Moreover, magnetite occurs commonly in South Africa, Germany, Russia and many places in the USA. This also exists in meteorites. Magnetite is important widely due to its magnetic properties. Further, it is a sorbent, so it is useful for water purification. Moreover, we can use it as a catalyst and a coating material.
What is Hematite?
This is the iron oxide, which contains Fe (3+) ion. Therefore, it has the molecular formula of Fe2O3. This is a mineral that can have several colours. Mineral has a subtranslucent or opaque nature. It occurs in red, brown, reddish brown, back or silvery colour. However, all these types of hematite minerals have the same reddish brown streak. In fact, hematite got its name because of the blood red colour it has when it is in the powder form.
Figure 02: A Red Colored Hematite Form
On the Mohs scale, its hardness is 5-6. Hematite is brittle, but it is harder than pure iron. Hematite has a rhombododecahedral crystal structure. This shows an irregular/uneven fracture. At lower temperatures hematite are antiferromagnetic. But at higher temperatures, it shows paramagnetism. There are few varieties of hematite as below.
- Hematite rose – a crystal arranged in the shape of a rose flower.
- Kidney ore – it has the appearance of kidney like masses.
- Tiger iron – these are very old deposits. The deposit has alternating layers of silver-grey hematite and red jasper.
- Specularite – this has a sparkling silver grey colour; therefore, useful as ornaments.
- Oolitic hematite – it contains rounded grains. It has a reddish brown colour and an earthy lustre.
Hematite occurs in England, Mexico, Brazil, Australia, and the Lake Superior region. It is important for jewellery and as ornaments.
What is the Difference Between Magnetite and Hematite?
Magnetite is an iron oxide with the chemical formula Fe3O4 whereas hematite is an iron oxide with the chemical formula Fe2O3. Magnetite iron is in +2 and +3 oxidation states whereas, in hematite, it is only in +3 oxidation state. This is the key difference between magnetite and hematite. Moreover, magnetite has higher iron content than hematite; therefore, its quality is higher.
Apart from that, in colours too, there is a difference between magnetite and hematite. Magnetite is black in colour, but hematite has a variety of colours. However, magnetite has a black streak, whereas hematite has a reddish brown streak. As another difference between magnetite and hematite, hematite is a component of rust, but magnetite is not. Moreover, when considering the magnetic properties of the two minerals, magnetite is a naturally strong magnet, but in hematite, magnetism occurs upon heating. In addition to that, one other difference between magnetite and hematite is their structure. Hematite has a rhombododecahedral crystal structure while, magnetite commonly shows octahedral crystal structure.
Summary – Magnetite vs Hematite
Magnetite and hematite are important oxides of iron. Though there are several differences between them, the key difference between magnetite and hematite is that the iron in magnetite is in +2 and +3 oxidation states whereas, in hematite, it is only in +3 oxidation state.
Reference:
1. “Magnetite.” Wikipedia, Wikimedia Foundation, 22 Sept. 2018. Available here
2. “Hematite.” Wikipedia, Wikimedia Foundation, 2 Oct. 2018. Available here
Image Courtesy:
1.”Magnetite-118736″ By Rob Lavinsky, iRocks.com (CC BY-SA 3.0) via Commons Wikimedia
2.”Hematite-rich BIF ventifact” By James St. John (CC BY 2.0) via Commons Wikimedia