How Tektites are formed by Meteorite Collision Impacts?
The word Tektite has been taken from a Greek word "Tektos or melted" . People have been having a kind of fascination about glass products since centuries. The glass found in Afghanistan is famous as "mountain glass" . Similarly is the case with Libyan Glass. It were Chinese around 900 BC , who described the tektites thoroughly. In a book of Liu Sun, during T' and dynasty, it was written (after translation)
“Notes on the Wonders Beyond the Nanling Mountains in Kwangtung”.
Tektite remained enigma still 1973. It was Alfred Lacroix, a researcher from the Musee National d’Histoire Naturelle, who described the Tektite technically right after finding large Tektite deposits in Indonesia. Later, another locality was found about Tektite deposits existed at Ivory Coast. These findings increased the interest of scientists about Tektites. The researchers started to define and test tektites. Some researchers linked the Tektite with the Moon.
Tektite has been linked with possibly extraterrestrial origins by the researchers and scientists. However, scientists believed that the stone is formed from melting and than rappid cooling of terrestrial rocks. Those rocks were vaporized by high energy impact of comets, asteroids or meteorites on the Earth's surface.
What is Tektite?
Tektites are basically glass. A silica glass formed by hypervelocity activity. Tektites occur due to hypervelocity meteorite collisions with terrestrial rocks on Earth's surface. The size of tektite is almost of walnut.
The refractive index of Tektites range from 1.48 to 1.51. The specific gravity is from 2.3 to 2.5. The tektite glass is almost anhydrous in contrast to volcanic glass. Tektite color and age can be different depending on the land or origin where they are found. The age of tektite usually goes from 35.5 million to 750,000 years old.
The chemical property of tektite consist on silica content. For example, the Australasian tektites would have 70% silica and Libyan glass will have 98%. They are further distinguished from granitic (acid igneous) rocks because of having lower soda content and potash. And also because of higher lime, magnesia and iron content. Tektite usually lack crystals, microlites, which is characteristics of terrestrial volcanic Glasses.
Mostly scientists think that tektites are formed by rapid heat and sudden cooling effects of quartz rich soils and rocks. Impact of meteorites or asteroids, the large terrestrial bodies are enough to melt soils, rocks, minerals and help in forming tektite.
Alternative Hypotheses about Tektite
Early researchers had opinion that tektites is a product of terrestrial volcanic eruption. Tektites took their shapes because of abrasion impacted by wind blown or water. However, later researches disapproved the theory by calling it not abraded. Though, apparently they will look similar to ablation.
We can see abrasion on gems also which are found in sedimentary rocks. Wind, rocks, water all play role to give specific shape to a rock or a gem. Ablation is different than Abrasion. It is a process of reshaping molten surface layers of meteorites by vaporizing during flight towards Earth's atmosphere.
There are many theories about tektite formation that how they were formed. Some even have views that tektites are actually man made products. But if we look at chemical properties, age, this disconnects such theories or beliefs. It is also because of age factor as human civilization techniques started or are found around 6000 B.C whereas tektite ages are more older than human civilization.
Properties of Tektites
- Distribution of age
- geological ag.
- Physical properties
- chemical compositions.
- Shape of tektites
- melting features of tektite specimens
- Internal features
Tektites are found across the Earth in specific areas which are called strewn fields. Such fields are found on every continent except Antarctica. They have been taking formation in a group at different times of Earth. The field of North American strewnfield is dated at 35.4million years ago. They are mostly splash form type. Czen Republic strewn field is dated 14.6 million years is having few tens of thousand tektite specimens. Some tektites are found in North American region are known as Moldavites. The Australasian strewnfields extends from South China.
Chemical Composition of Tektites
Hardness of Tektites: 6 to 7 on Mohs' scale
Tektites have mostly have silica (SiO2) content. Silica content range is different from moldavite, Libyan glass or ivory coast tektites.
Though obsidian also has high content of silica such as up to 80%. However, there are various other features which can differ obsidian from tektites.
Tektites often includes tiny particles of lechatelierite. Which is very rare silica glass can only be formed by melting of quartz crystals within extreme high temperatures and pressures. Such properties guide us towards recognition of tektite as a result of meteorite impacted events. Such particles are not found in obsidian or naturally occurring glass. Air bubbles are associated with lechatelierite which indicates specific pressure enough to form lechatelierite.Division of Tektites
Tektite Formula: Silica (75%) + Al, Fe, Ca, Na, K, Mg, Ti, Mn.
Transparency: Transparent to Opaque
Optics: Isotropic; N = 1.46-1.54.
Color: Blackish Yellow, Green, Greenish Brown, Brownish Yellow, Brown in Moldavites, greenish yelloww, colorless.
Crystallography: Amorphous (tektites are natural glasses).
Division of Tektites
- Darwin Glass
Types of Tektites
Tektites are distributed in following types on the external form basis.
Type B is a “splash-form” tektites. Such types are found in shape of spheres, ellipsoids, rods, teardrops, dumbbells, and boats.Their internal structure show contoured, rolled or bent because of fluid flow while being molten.
Such type of tektites appears by heat on one side. Portion of the mass is lost to ablation or resculpted to form a flange derived from anterior side's material. These are common Australites. They are also found in Javanites.