What is the Difference Between Pumice and Scoria

The main difference between pumice and scoria is that pumice appears in light colours, whereas scoria appears in dark colours.

Pumice and scoria are two types of volcanic rocks that may or may not contain crystals. Volcanic rocks are a type of rock that forms from the lava erupted from a volcano. We can easily distinguish pumice from scoria based on their appearance.

Key Areas Covered

1. What is Pumice
     – Definition, Characteristics, Formation
2. What is Scoria
     – Definition, Characteristics, Formation
3. What is the Difference Between Pumice and Scoria
    – Comparison of Key Differences

Key Terms

Pumice, Scoria, Volcanic Rocks

What is Pumice

Pumice or pumicite is a type of volcanic rock that may or may not contain crystals and has a highly vesicular texture. We can find this material usually in a powdered, dust form. It has a rough texture. Typically, pumice is light coloured; e.g. light yellow colour.

Figure 1: Pumice

Generally, pumice has very small vesicles. Moreover, the walls of these vesicles are comparatively thin. However, pumice is less dense than scoria rock. Pumice rocks are created when super-heated and highly pressurized rocks are violently ejected from volcanoes. Pumice rocks have an unusual foamy appearance. This foamy appearance is created due to rapid cooling and rapid depressurization. Bubbles created from rapid depressurizing lowers the solubility of gases that can dissolve in lava. Then these gas bubbles tend to rapidly exsolve. Thereafter, these bubbles get trapped and frozen in the matrix, giving the pumice rock a foamy texture.

Pumice typically has a siliic or felsic to intermediate composition. The colour of pumice rocks can vary from white, cream, grey, yellow to brown. This rock type is a common product of volcanic eruptions. The porosity of pumice rock is about 64-85%. Generally, pumice has two types of vesicles: tubular microvesicles and subspherical vesicles.

What is Scoria

Scoria is a type of volcanic rock that may or may not contain crystals and appears in a dark colour. These rocks are highly vesicular. Relatively, scoria has a low density due to the presence of numerous macroscopic ellipsoidal vesicles. However, it sinks in water and has a density higher than pumice. The specific gravity of this rock is higher than 1.0.

The vascular structure of scoria arises due to the release of gases that are dissolved in magma when magma comes out of a volcano during an eruption. This creates bubbles in the molten rock which get frozen when the rock solidifies.

Figure 2: Scoria

There are some uses of scoria; for example, it is used in landscaping and drainage works due to the foamy texture and light colour. It is also important in gas barbecue grills. In addition, we can use it for high-temperature insulation.

Difference Between Pumice and Scoria

Definition

Pumice or pumicite is a type of volcanic rock that may or may not contain crystals and has a highly vesicular texture while scoria is a type of volcanic rock that may or may not contain crystals and appears in a dark colour.

Appearance

While pumice is light coloured, scoria is dark coloured.

Density

Pumice has a low density when compared to scoria.

Vesicles

Pumice has small vesicles while scoria has large vesicles.

Vesicle Walls

Moreover, pumice has thin vesicle walls while scoria has thick vesicle walls.

Conclusion

Pumice and scoria are two types of volcanic rocks that may or may not contain crystals. Volcanic rocks are a type of rock that form from the lava erupted from a volcano. Moreover, we can easily distinguish pumice from scoria based on their appearance. The key difference between pumice and scoria is that pumice appears in light colours, whereas scoria appears in dark colours.

Reference:

1. Pumice.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 20 Jan. 2020, Available here.
2. “Pumice.” Wikipedia, Wikimedia Foundation, 28 May 2020, Available here.
3. “Scoria.” Wikipedia, Wikimedia Foundation, 5 June 2020, Available here.

Image Courtesy:

1. “Teidepumice” By User MPF on en.wikipedia – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Scoria Macro Digon3” By I, Jonathan Zander (CC BY-SA 3.0) via Commons Wikimedia