Meteorites are usually divided into three categories according to their internal iron and nickel metal content: stony meteorites, iron meteorites, and stony iron meteorites. The iron and nickel metal content in the stone meteorite is less than or equal to 30%. The iron and nickel metal content of stony iron meteorites is between 30% and 65%. The iron and nickel metal content of iron meteorites is greater than or equal to 95%. Glass meteorites do not contain metal components.
Most meteorites are chondrites (91.5% of the total), of which ordinary chondrites are the most (80% of the total). The chondrite is characterized by a large number of millimeter to sub-millimeter silicate spheres inside (see picture). Chondrites are the most primitive matter in the solar system, and are directly condensed from the primitive solar nebula. Their average chemical composition represents the chemical composition of the solar system. The largest stony meteorite in the world is the Jilin Ordinary Chondrite that fell in my country's Jilin Province in 1976. The No. 1 meteorite weighs about 1770 kg.
Achondrites, stony-iron meteorites, and iron meteorites are collectively called differentiated meteorites. They are the products of the differentiation and crystallization of chondrites through high-temperature melting, and represent samples of different levels within asteroids. The internal structure of these asteroids is similar to that of the Earth. It is divided into three layers, with an iron core (iron meteorite) in the center, a stone-iron mixed mantle layer (stony-iron meteorite) in the middle, and a stone-based crust (achondrite) in the middle. Meteorite). The largest iron meteorite in the world is the Hoba iron meteorite from Namibia, Africa, weighing 60 tons. The iron meteorite found in Yinniugou, Qinggou County, Altay Region, Xinjiang, weighs about 28 tons and is the third largest iron meteorite in the world.