Meteorite refers to the residual core that meteoroids reach the surface after melting from interstellar space through the atmosphere. Meteorites come in all shapes and sizes. Generally, there is a very thin black or dark brown molten shell (less than 1mm) on the surface of meteorites, which is formed by melting the surface at high temperature during falling in the atmosphere and cooling and solidifying when the speed decreases.
Generally speaking, meteorites are divided into three categories: stone meteorites, iron meteorites and stone iron meteorites. Stone meteorite is a meteorite dominated by silicate minerals, iron meteorite is a meteorite dominated by iron and nickel metals, and stone meteorite is a meteorite with half iron and half stone. According to the presence or absence of chondrites, stone meteorites can be further divided into relatively primitive chondrites and differentiated chondrites.
1) Stone meteorite: It is the most abundant falling meteorite, similar to some rocks on the earth, but the weight of stone meteorite is slightly heavier. If the meteorite is not broken for a long time, bright silver metallic iron particles and silicate chondrules with more content can be observed in the most common ordinary chondrites.
2) Iron meteorites: Iron meteorites are mainly composed of iron and nickel, with irregular shape, high density and strong magnetism. Some fresh iron meteorites have some "fingerprint" structures on their surfaces. Below are some pictures of iron meteorites.
3) Stone-iron meteorites: There are relatively few stone-iron meteorites, mainly including iron meteorites and olive meteorites. Olive meteorite is mainly composed of light green yellow olivine crystals and iron-nickel matrix. In other words, iron meteorites are composed of massive and veined metals, without chondrite basalt and glass matrix.
What is a diamond?
The chemical composition of diamonds is carbon, which is the only single element in gems. It belongs to the equiaxed crystal system. The crystal forms are mostly octahedron, rhombic dodecahedron, tetrahedron and their aggregates. Pure diamond is colorless and transparent, showing different colors due to the mixing of trace elements. Strong diamond luster. The refractive index is 2.4 17 and the dispersion is moderate, which is 0.044. An isotropic object. The thermal conductivity is 0.35 calories/cm sec .. Tested by thermal conductivity meter, the response is the most sensitive. The hardness is 10, which is the hardest mineral known at present. The absolute hardness is 1000 times that of the time, and 150 times that of corundum. It is afraid of heavy blows, and it will be broken by cleavage after heavy blows. A set of cleavage is completed. The density is 3.52g/cm3. Diamonds are luminous, and when the sun shines,
, can emit light cyan phosphorescence at night. X-ray irradiation emits sky blue fluorescence. The chemical properties of diamond are very stable, and it is not easy to dissolve in acid and alkali at room temperature, and acid and alkali will not affect it.
What is the night pearl?
"Night Pearl" is a kind of natural gem, which can be seen clearly by human eyes in the dark and can glow by itself. From the point of view of solid state physics, the matrix materials of the mineral "night pearl" are all active crystalline phosphors in inorganic salts. The so-called active crystalline phosphor refers to the crystal that has the ability of "emitting light" due to the lattice distortion of the crystal lattice, and this distortion is mostly caused by some heavy metal impurities (activators) contained in the matrix. For example, a small amount of cu in zns can emit yellow-green phosphorescence, which is called matrix and cu is called activator.
At present, there are more than 100 phosphors in common use, and their chemiCal components are all divalent metals (ca. SRBA。 CD. Mg。 Zinc. )-Sulfide, selenide, telluride, silicate, aluminate, tungstate, phosphate and halophosphate.
Due to the different activators in active crystalline phosphors, active crystalline phosphors, namely "luminous pearls", can be divided into two categories:
(1) Permanent luminous luminous luminous luminous pearl: It does not need any external energy excitation, but contains an activator, such as 14c. ..
3h。
147pm。
Radioisotope, such as 226 ra. 232nd Street. Can self-excite light.
② Long-lasting luminous night pearl: The activator in the phosphor is not radioactive, and it can only emit light after being excited by external sunlight, ultraviolet rays and other light sources.