Pumice rock is a light-colored igneous rock, which is formed from the magma or lava of a volcano. In other words, it is a pyroclastic (cooled magma), having large concentrations of silica. It has a vesicular texture, as a result of gas trapped in the melt at the time of magma or lava solidification. Unlike other rocks, pumice stone can float on water. However, it eventually gets waterlogged, and sinks. It is considered as a whipped glass, as it has a similar chemical composition as that of obsidian (a volcanic glass), and is light enough to float on the water. The term pumice is derived from a Latin word pumex, which means foam, and refers mainly to large pieces of the rock. On the other hand, pumicite refers to pieces ranging from ash to small grain sizes.
Some Facts about the Pumice Rock
- Normally, this porous rock is light brown or grayish in color.
- However, it does exist in various other colors like white, shades of gray, reddish black, or black.
- It may also have bands of colors.
- Lighter the color, higher is the amount of silica in it.
- The rock may also have small lines on it, due to the lava motion at the time of cooling.
- Pumice is formed during explosive volcanic eruptions, and contains any type of magma or lava (andesite, basalt, dacite, rhyolite).
- The rock formation takes place when the gas bubbles, called vesicles, get trapped in the molten magma.
- The pressure on the magma decreases when it flows upward to the areas of lower pressure, keeping the gases compacted.
- Further decrease in the pressure solidifies the molten magma, due to which the bubbles get trapped.
- When the magma cools, the molecules don't have enough time to form crystal structures. As a result, they end up forming porous glass.
- Another method of formation is when the molten rock converts water to penetrating steam.
- A fine-grained version of pumice, called pozzolan, when combined with lime, is used to make lightweight concrete mix, or insulative, low-density concrete blocks.
- Another industrial application is that pumice can be used to wash jeans in washing machines, to give a worn look.
- Pumicite is used as an abrasive in polishes, pencil erasers, toothpastes, hand cleaners, cosmetic exfoliants, etc.
- One of the most common uses of the rock is to soften and smoothen rough, callused feet. It exfoliates and removes dead or dry skin.
- It is widely used to remove excess hair from legs, arms, and other sensitive areas of the body. However, before using it, ensure that your skin is wet, and a bit soapy. Later, don't forget to use a moisturizer.