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Pumice: Types of Vesicles
Pumice
Pumice in its powdered or dust form is known as pumice. It is a very porous, froth-like volcanic glass. It consists of a highly vesicular rough texture, which may or may not contain crystals. Typically it has a light-color. Other than pumice there is another vesicular volcanic rock, Scoria. But it differs from pumice as it has larger vesicles, thicker vesicle walls, dark color, and is denser.
Formation of Pumice
It forms when super-heated and highly pressurized rock violently erupt from a volcano. It is spumy because of concurrent rapid cooling and rapid depressurization. However, this depressurization creates bubbles by lowering the solubility of gases (including water and CO2). Also, it dissolves in the lava, causing the gases to rapidly exsolve (like the bubbles that appear when we open a carbonated drink). The concurrent cooling and depressurization freeze the bubbles in a matrix.
Properties of Pumice
It mainly consists of highly microvesicular glass pyroclastic with very thin, translucent bubble walls of extrusive igneous rock. Also, it is usually pale in color and ranges from white, cream, blue or grey, to green-brown or black. It forms when volcanic gases come out from viscous magma.
This gas then forms bubbles that remain within the viscous magma and cools to form glass. It has a porosity of 64–85% by volume and it floats on water, possibly for years, until it eventually sinks. It is considered volcanic glass because it has no crystal structure. Pumice vary in density depending on the thickness of the solid material between the bubbles.
Types of Vesicles
There are two main forms of vesicles. Besides, most of it has tube-like microvesicles that can tear apart a silky or fibrous fabric. The other form of vesicles are subspherical to spherical and result from high vapor pressure during the eruption.
Location of Vesicles
We can find it all around the globe deriving from continental volcanic occurrences and submarine volcanic occurrences. Also, the ocean current distributes the floating stones. As we know it is produced by the eruption of explosive volcanoes under certain conditions, therefore, natural sources occur in volcanically active regions.
Asia – Asian countries including Afghanistan, Indonesia, Japan, Syria, Iran, and eastern Russia has large reserves of pumice. There are 19 active volcanoes in this area and it lies in close proximity with the Pacific volcanic belt.
Europe – Europe produces an enormous quantity of pumice with deposits in Italy, Turkey, Greece, Hungary, and Iceland. Italy leads in producing pumice because of its numerous eruptive volcanoes.
America – Chile is again one of the largest producers of pumice in the world. It is also found all across North America including the Caribbean Islands.
Australia – In July 2012, the Havre Seamount volcano started to erupt and produced the largest-known deep ocean volcanic eruption on Earth. In addition, most of this floating pumice get deposited on the North-West coast of New Zealand and the Polynesia islands.
Uses of Pumice
Early medicine – For more than 2000 years pumice has been in use in the medicinal industry. Along with other ingredients, it is useful to treat dizziness, nausea, insomnia, and anxiety disorders. It is also useful to treat ulcers mostly on the skin and cornea.
Horticulture – Pumice improves the quality of soil because of its porous properties. It can easily transport water and gases through the pores. Also, it can store nutrients in microscopic holes. Often we use it on roadsides and ditches. Commonly we use it in turf and golf courses to maintain grass cover and flatness that can degrade due to large amounts of traffic and compaction.
Personal care – In its powder form humans use it to whiten teeth in ancient Rome. It is widely in use as a skin exfoliant. Beauty salons use pumice stones during the pedicure process to remove dry and excess skin from the bottom of the foot as well as calluses.
Others – It is useful for water filtration, chemical spill containment, cement manufacturing, horticulture, etc. As it is abrasive in nature, it is also useful in polishes, pencil erasers, and in the production of stone-washed jeans.
Examples:
Question 1.
What minerals are in pumice?
Answer:
Small crystals of various minerals occur in many pumices; the most common are feldspar, augite, hornblende, and zircon. Moreover, the cavities (vesicles) of it are sometimes round and they can also be tubular or long, depending on the flow of the solidifying lava.
Question 2.
What is the melting point of pumice?
Answer:
The melting temperature of Pumice Stone is 15000˚C and pH value is 8 and the density is 2.313g/cm3.