Is Granite Magnetic ? 5 Facts You Should Know !

Granite belongs to a large family of rocks called granitoid, composed of quartz, alkali feldspar, and plagioclase. Now, let us know about one of the basic properties, the magnetism of granite.

Granites exhibit non-magnetic behaviors due to a lack of free charges and metal ions in the granite structure. But some iron-rich granite rocks can exhibit weak magnetism. Usually, dark granite has traces of magnetic material, so they exhibit weak magnetic behavior.

Granite consists of silica and alumina as the main compound, which is nonmagnetic. Thus rock granite shows no response to the magnetic field. Now, let us give some interesting facts regarding the magnetic properties of granite in this post.

Magnetic susceptibility of granite

The ability of a substance to be magnetized when exposed to an external magnetic field defines magnetic susceptibility. Let us know the magnetic susceptibility of granite.

The granite’s magnetic susceptibility varies from 1×10-6 to 4000×10-6 SI units, and some shows susceptibility up to 10-2 SI units. The bulk chemistry and magnetic mineralogy specify the susceptibility of rock granite. The variation of granite susceptibility helps distinguish between magnetic and nonmagnetic granite.

The magnetic susceptibility of granite from the iron-bearing silicates indicates that granite is paramagnetic. Variscan granite is a type of granite that has the lowest value of magnetic susceptibility of 10-6 SI units.

Is black granite magnetic?

Black granite is a hard intrusive igneous rock similar to basalt composed of calcic plagioclase. Let us know whether black granite is magnetic or not.

Black granite is magnetic but exhibits weak magnetism. Black granites are composed of more than one mineral and are rich in iron content which contributes to weak magnetism in black granite. The presence of minerals in granite makes a particular part of granite surrounded by the minerals slightly magnetic.

Can granite be magnetic?

Any material is said to be magnetic if any external magnetic field magnetizes it. Let us check whether granite can be magnetized or not.

A rock granite cannot be magnetic because its chemical makeup does not contain minerals. But in a uniform magnetic field, some granite can nearly be magnetized due to the isolation of mineral ions. The magnetic behavior of the minerals in the graphite rock leads to paramagnetic and ferromagnetism in granite.

Rock granite by James St. John (CC BY 2.0) from Wikimedia commons

Granite magnetic properties

Granite is hard and massive rock with a wide range of applications in engineering and construction. Let us list out some magnetic properties exhibited by granite.

  • Typical granite is nonmagnetic, but some granites can exhibit paramagnetic as well as ferromagnetic behavior.
  • The magnetic field of granite is lower than normal.
  • The presence of minerals contributes to the susceptibility of granite.
  • The primary permeability of granite is too poor, but its secondary permeability is strong.

Conclusion

Let us end this post by stating that a granitic rock with more magnetite exhibits ferromagnetic behavior and a less or negligible amount of magnetite exhibits paramagnetic behavior. The granitic rocks without magnetite or nonmagnetic minerals are purely nonmagnetic.

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