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Chondrules in the chondrite classification Grassland. A millimeter scale is shown. Chondrules in the Carbonaceous Chondrite NWA 13887. A chondrule (from Ancient Greek χόνδρος chondros, grain) is a round grain found in a chondrite. Chondrules form as molten or partially molten droplets in space before being accreted to their parent asteroids.
As petrologic type increases from type 3.1 through 3.9, profound mineralogical changes occur, starting in the dusty matrix, and then increasingly affecting the coarser-grained components like chondrules. Type 3.9 chondrites still look superficially unchanged because chondrules retain their original appearances, but all of the minerals have been ...
The meteorite of the type locality Ivuna in Tanzania fell in 1938 splitting into three pieces of altogether 705 grams (24.9 oz). This was followed in 1965 by a very bright fall in Revelstoke, British Columbia, but only two tiny fragments of 1 gram (0.035 oz) were found. All in all roughly 17 kilograms of CI-chondrites exist so far.
[3] In 2006 a classification was published that assigned 7 groups to the primitive achondrites, but the classification remains controversial. The authors define primitive achondrites as meteorites "that exceeded their solidus temperature on the parent body" and thus would partially melt. Meteorites that have been fully melted are included if ...
Many CM chondrules are surrounded by either rims of accessory minerals, or haloes of water-altered chondrule material. [29] [30] The chondrules of CM chondrites, though fewer, are larger than in COs. While CM chondrules are smaller than average in diameter (~300 micrometer), CO chondrules are exceptionally small (~170 um).
[1] [4] Entries in the catalogue are designated with a "C" and the catalogue number (1 to 109). Unlike objects in the Messier catalogue, which are listed roughly in the order of discovery by Messier and his colleagues, [ 5 ] the Caldwell catalogue is ordered by declination , with C1 being the most northerly and C109 being the most southerly ...
The RCW Catalogue (from Rodgers, Campbell & Whiteoak) is an astronomical catalogue of Hα-emission regions in the southern Milky Way, described in (Rodgers et al. 1960).It contains 182 objects, including many of the earlier Gum catalogue (84 items) objects.
Somewhat more than 10% of the rock is composed of metal grains. A diagnostic feature of EH chondrites is that the Fe-Ni metal contains ~3 wt% elemental silicon. EL (low-iron) chondrites contain larger chondrules (>0.5 millimetres (0.020 in)), and low ratios of siderophile elements to silicon. Fe-Ni metal contains ~1 wt% silicon.