"Minerals A to Z"




























Meteorites are naturally occurring objects that originate in space and survive a fall to the ground through Earth's atmosphere. Most are remnants of asteroids or possibly comets. However, a few have been shown to be pieces of Moon or Mars that were launched into space by an impact event. While moving through space these objects are known as meteoroids. The bright streaks that they produce while moving through Earth's atmosphere are known as a meteors.

The term meteorite is also used for a meteoroid that has landed on the surface of a celestial body other than earth.

There are three main types of meteorites. The most abundant are stone meteorites which are primarily made up of silicate minerals such as olivine, pyroxene and feldspar. As their name implies, iron meteorites are mainly composed of iron but also contain a significant amount of nickel. The rarest of the three are the stony-iron meteorites. They are a mixture of stony and metallic materials.


Tektites are found in geographically restricted areas and are associated with asteroid or comet impact with the Earth. A number of previous hypotheses were put forward, including a lunar origin (from lunar volcanoes or lunar impact events). These alternatives are no longer taken seriously by scientists. It has been firmly established that tektites are terrestrial rock melted and flung into the atmosphere by the force of an asteroid or comet impact.

Tektites are found in many shapes and sizes. The different morphologies are geographically restricted and occur in a radial pattern away from the source crater. It is then attempted to deduce what the morphologies and surface sculptures tell us about the formation of tektites. Tektites are made of glass, and it is the properties of glass which are so important in understanding the final forms we see today. Some controversy and misunderstanding still surrounds tektites, but finally we are getting to the truth and dispelling the myths. There is always more to be learnt though, so long live the debate: it is the enigmatic nature of tektites that makes them so appealing!


Moldavites have been shown to be about 14.7 million years old. The most popular explanation of their origin, according to Prof. Bouska, is that they were formed during the impact of a large meteorite, or comet nuclei, with the Earth’s surface. He explains the formation of tektites in simplified terms: “An enormous body with a volume of several cubic kilometers is racing towards the Earth. The uppermost layers of the Earth’s surface are melted by the highly compressed hot air cushion in front of the flying meteorite prior to its contact with the surface of the Earth. At the moment of impact, there is a tremendous explosion comparable with a multiple hydrogen bomb, the atmosphere is torn apart, and tektites are formed in the vacuum bubble. The fusion process and the throwing out of the tektite glass material occurs in a very short time period prior to the actual impact of the meteorite or comet core. The modeling of the formation of large impact craters has shown that the column of hot ascending atmosphere can carry the tektite melt into the upper parts of the atmosphere or even above the atmosphere.” A search was made, worldwide, for meteorite craters in the vicinity of tektite strewnfields. There is strong evidence to support this explanation of the origin of tektites due to the known age of tektites found in certain areas, and the relative proximity of the tektite strewnfields to large meteorite craters of the same age. A number of researchers have suggested that the surface material in the area around the Ries Crater, in Germany, is probably the source material for Moldavites -- the age of the crater is identical with the age of Moldavites.


The Sikhote-Alin iron meteorite is the largest observed meteorite fall in modern history. It rained a shower of fireballs into the thick forest of the Sikhote-alin Mountains in Eastern Siberia of Russia on February 12, 1947 at 10:38 hours. The flaming fireball, as bright as the sun, cast moving shadows in broad daylight as it passed by observers. It is estimated that over 23000kg fell that morning leaving a smoke trail which could be seen in the sky for hours. The meteorite impacted the mountains with a huge explosion which was felt over 100 miles away. It made over 120 craters of varying sizes. The largest reported crater was 20 feet deep and 85 feet across. When the main mass exploded, it blasted fragments in every direction. Pieces were even found embedded in nearby trees.

There are two types of Sikhote-Alin meteorites: sharp, jagged shrapnel type specimens and the more beautiful individuals covered in regmaglypts. These magnificent thumbprinted specimens display a beautiful steel-blue fusion crust. The appearance of Sikhote-Alin individuals is typical of what the general public believes a meteorite should look like.


This Nantan meteorite, an iron meteorite, was named after the place where it was found in southern China. The fall was recorded as being in 1516 -- " During summertime in May of Jiajing 11th year, stars fell from the northwest direction, five to six fold long, waving like snakes and dragons. They were as bright as lightning and disappeared in seconds". The nantan meteorite was discovered by the local residents of Nandan, China when they tried to melt them, assuming by the weight that they were iron ore. They brought them for processing and to their surprise they would not melt. It was then studied by the government and decided that these VERY heavy rocks were actually iron meteorites with a composition of approximately 85% iron and 6-7% nickel.