Difference Between Mafic vs Felsic

If you are a geology student, you have probably had to figure out the difference between mafic and felsic. Indeed, those terms are commonly used to describe kinds of rocks. If you are reading this piece because you do not know their dissimilarities, don’t sweat it.

In this article, you will learn about the terms and how they relate to viscosity, density, color, mineral content, silica level, and more. In our usual way of starting our comparison articles, we will begin this topic by defining the terms, comparing their features, and wrapping up the guide. Continue reading to learn more.

Definition of Mafic

Mafic is an acronym for magnesium and ferric, which refers to iron. Igneous rock is rich in the two metals. Igneous rock itself is born in volcanic eruptions. Coming to the color, the rock typically exists in green or greenish-black appearance. However, some of the examples that fall into this group have a grey color.

Noteworthy is that its texture has a medium to coarse feeling. With the presence of silica, it always exhibits a relatively high density. Thanks to the low viscosity of lava, the eruption is usually runny. It is also important to point out that the runny nature explains the amount of silica in it. Good examples of rocks that fall into this group are gabbro, basalt, and dolerite.

These rocks contain minerals like amphibole, olivine, and biotite. With silica content taking up to 50% of the weight of these rocks, they cool too quickly to form crystals. Plus, they have a specific gravity that is greater than 3. It goes without saying that these rocks must be extremely hot to melt or have a high melting point.

Definition of Felsic

Felsic is a term used to describe an igneous rock that is rich in feldspar and silica. But then, feldspar is the name used to describe a mineral with an extremely high amount of silica and aluminum. Better still, it is a term used to describe silicate materials. The densities of rocks that fall into this group are very low and come with light colors.

Other common features of rocks that are grouped here are those that contain high amounts of oxygen (O₂), aluminum (Al), potassium (K), and sodium (Na). Because these elements dominate the contents of these rocks, they often have a lighter color. In a similar vein, the abundance of those elements explains its characteristic lightness. Well, good examples of rocks that fall into this group are granite, quartz, and muscovite.

Indeed, a meticulous analysis of the contents of those examples mentioned above shows that they contain high amounts of silica. For instance, granite is 70% silica. It is worthwhile to note that their melting points are usually low. Additionally, their specific gravities are always less than 3. Having come thus far, let us look at the difference between felsic and mafic in detail.

Main Differences Between Mafic vs Felsic

The table below gives more insight into felsic vs mafic.

Basis of comparison	Mafic	Felsic
Lava viscosity	High temperature of lava leads to extremely low viscosity	The level of viscosity is extremely high
Density	It is very heavy and has a high density	It is lightweight, and the density is low
Color	It often has colors like black, grey, and green	It usually has light colors
Content	It is rich in magnesium and iron	It is rich in silica and feldspar. Hence, it is called a silicate material
Level of silica	The level of silica is between 45% and 55%	The level of silica is between 70% and 85%
Examples	Gabbro, basalt, and dolerite	Granite, quartz, and muscovite

Difference Between Mafic and Felsic: Conclusion

In conclusion, you have seen the most significant points in mafic vs felsic. For a quick summary, the disparity between them is obvious in their levels of viscosity. While the former is created in high-temperature lava that leads to extremely low viscosity, the latter has a high viscosity. Another point to emphasize is that mafic has a lower level of silica (45% to 55%) whereas felsic has a higher level of silica (70% to 85%).